Showing papers on "Dynamic pressure published in 2009"

Dynamic interface pressure distributions of two transtibial prosthetic socket concepts.

Abstract: In this study, we investigated and compared the dynamic interface pressure distribution of hands-off and hands-on transtibial prosthetic systems by means of pressure mapping Of the 48 established unilateral amputees recruited, half (n = 24) had been wearing pressure-cast prostheses (IceCast Compact) and the other half (n = 24) had been wearing hand-cast sockets of the patellar tendon bearing design We measured the dynamic pressure profile of more than 90% of the area within each prosthetic socket by means of four Tekscan F-Scan socket transducer arrays We compared the interface pressure between socket concepts We found that the distribution of dynamic pressure at the limb-socket interface was similar for the two intervention (socket prescription) groups However, a significant difference was found in the magnitude of the interface pressure between the two socket concepts; the interface pressures recorded in the hands-off sockets were higher than those seen in the hands-on concept Despite the differences in interface pressure, the level of satisfaction with the sockets was similar between subject groups The sockets instrumented for this study had been in daily use for at least 6 months, with no residual-limb health problems

Acoustics, Vortex Shedding, and Low-Frequency Dynamics Interaction in an Unstable Hybrid Rocket

Abstract: This paper deals with an experimental investigation into the stability behavior of a hybrid rocket where gaseous oxygen is fed with either an axial conical subsonic nozzle or a radial injector. The influence of the oxidizer-injection configurations on the motor stability is thoroughly examined. These distinct oxidizer-injection techniques allowed unveiling key and so far unreported features of the hybrid rocket combustion stability, especially emphasizing the role of vortex shedding which occurs in both the pre- and postcombustion chamber. Axial and radial injectors caused completely stable and unstable combustor operations, respectively, and this fact has been attributed to the fluid dynamics and unsteady heat release at the entrance of the fuel grain port. In particular, the unstable combustion in the radial-flow injector motor was dominated by low-frequency pressure oscillations, around 10-20 Hz. These low-frequency pressure oscillations were always accompanied by longitudinal acoustic modes. In some cases, the pressure oscillations abruptly increased, reaching peak-to-peak amplitude close to 70% of the mean chamber pressure, which is somewhat unusual for hybrid engines. Vortex shedding in the aft-mixing chamber is considered as the main driving mechanism of this latter behavior.

Properties of subsonic open cavity flow fields

Abstract: Flow over an open cavity was studied for several different subsonic free stream Mach numbers ranging from 0.19 to nearly 0.73. Velocity field information was acquired through an application of particle image velocimetry, while the fluctuating surface pressure was acquired through a linear array of surface pressure sensors. These data were acquired on the centerline of the cavity which had a length to depth ratio of 6 and a turbulent boundary layer upstream of its leading edge. Over the range of free stream Mach numbers the fluctuating surface pressure spectra in the cavity exhibited different behavior ranging from no apparent resonance to resonance being dominated by the second or third Rossiter modes. The broadband levels of surface pressure spectra with strong resonant tones collapse with scaling by the flow dynamic pressure. Velocity measurements reveal that the center of circulation of the flow within the cavity moves from the aft wall towards the center of the cavity with increasing Mach number. The trend in the mean flow was also apparent in the mean square fluctuating velocities although to a lesser extent. Application of the proper orthogonal decomposition was performed independently on the velocity fields from each of the different free stream cases yielding a spatially dependent basis set. Using a similarity parameter between these spatial orthogonal basis functions it was shown that the first two modes for all of the cases were quantitatively similar. Furthermore this analysis showed some higher less energetic modes that were similar between the cases.

Magnetospheric cavity modes driven by solar wind dynamic pressure fluctuations

Abstract: [1] We present results from Lyon-Fedder-Mobarry (LFM) global, three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere interaction. We use these simulations to investigate the role that solar wind dynamic pressure fluctuations play in the generation of magnetospheric ultra-low frequency (ULF) pulsations. The simulations presented in this study are driven with idealized solar wind input conditions. In four of the simulations, we introduce monochromatic ULF fluctuations in the upstream solar wind dynamic pressure. In the fifth simulation, we introduce a continuum of ULF frequencies in the upstream solar wind dynamic pressure fluctuations. In this numerical experiment, the idealized nature of the solar wind driving conditions allows us to study the magnetospheric response to only a fluctuating upstream dynamic pressure, while holding all other solar wind driving parameters constant. The simulation results suggest that ULF fluctuations in the solar wind dynamic pressure can drive magnetospheric ULF pulsations in the electric and magnetic fields on the dayside. Moreover, the simulation results suggest that when the driving frequency of the solar wind dynamic pressure fluctuations matches one of the natural frequencies of the magnetosphere, magnetospheric cavity modes can be energized.

Behaviour of an air-assisted jet submitted to a transverse high-frequency acoustic field

Abstract: Acoustic instabilities with frequencies roughly higher than 1 kHz remain among the most harmful instabilities, able to drastically affect the operation of engines and even leading to the destruction of the combustion chamber. By coupling with resonant transverse modes of the chamber, these pressure fluctuations can lead to a large increase of heat transfer fluctuations, as soon as fluctuations are in phase. To control engine stability, the mechanisms leading to the modulation of the local instantaneous rate of heat release must be understood. The commonly developed global approaches cannot identify the dominant mechanism(s) through which the acoustic oscillation modulates the local instantaneous rate of heat release. Local approaches are being developed based on processes that could be affected by acoustic perturbations. Liquid atomization is one of these processes. In the present paper, the effect of transverse acoustic perturbations on a coaxial air-assisted jet is studied experimentally. Here, five breakup regimes have been identified according to the flow conditions, in the absence of acoustics. The liquid jet is placed either at a pressure anti-node or at a velocity anti-node of an acoustic field. Acoustic levels up to 165 dB are produced. At a pressure anti-node, breakup of the liquid jet is affected by acoustics only if it is assisted by the coaxial gas flow. Effects on the liquid core are mainly due to the unsteady modulation of the annular gas flow induced by the acoustic waves when the mean dynamic pressure of the gas flow is lower than the acoustic pressure amplitude. At a velocity anti-node, local nonlinear radiation pressure effects lead to the flattening of the jet into a liquid sheet. A new criterion, based on an acoustic radiation Bond number, is proposed to predict jet flattening. Once the sheet is formed, it is rapidly atomized by three main phenomena: intrinsic sheet instabilities, Faraday instability and membrane breakup. Globally, this process promotes atomization. The spray is also spatially organized under these conditions: large liquid clusters and droplets with a low ejection velocity can be brought back to the velocity anti-node plane, under the action of the resulting radiation force. These results suggest that in rocket engines, because of the large number of injectors, a spatial redistribution of the spray could occur and lead to inhomogeneous combustion producing high-frequency combustion instabilities.

Aerodynamics of a Gulfstream G550 Nose Landing Gear Model

Abstract: In this paper we discuss detailed steady and unsteady aerodynamic measurements of a Gulfstream G550 nose landing gear model. The quarter-scale, high-fidelity model includes part of the lower fuselage and the gear cavity. The full model configuration allowed for removal of various gear components (e.g. light cluster, steering mechanism, hydraulic lines, etc.) in order to document their effects on the local flow field. The measurements were conducted at a Reynolds number of 7.3 x 10(exp 4) based on the shock strut (piston) diameter and a freestream Mach number of 0.166. Additional data were also collected at lower Mach numbers of 0.12 and 0.145 and correspondingly lower Reynolds numbers. The boundary layer on the piston was tripped to enable turbulent flow separation, so as to better mimic the conditions encountered during flight. Steady surface pressures were gathered from an extensive number of static ports on the wheels, door, fuselage, and within the gear cavity. To better understand the resultant flow interactions between gear components, surface pressure fluctuations were collected via sixteen dynamic pressure sensors strategically placed on various subcomponents of the gear. Fifteen of the transducers were flush mounted on the gear surface at fixed locations, while the remaining one was a mobile transducer that could be placed at numerous varying locations. The measured surface pressure spectra are mainly broadband in nature, lacking any local peaks associated with coherent vortex shedding. This finding is in agreement with off-surface flow measurements using PIV that revealed the flow field to be a collection of separated shear layers without any dominant vortex shedding processes.

Mars Entry Atmospheric Data System Modelling and Algorithm Development

Abstract: The Mars Entry Atmospheric Data System (MEADS) is being developed as part of the Mars Science Laboratory (MSL), Entry, Descent, and Landing Instrumentation (MEDLI) project. The MEADS project involves installing an array of seven pressure transducers linked to ports on the MSL forebody to record the surface pressure distribution during atmospheric entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. In particular, the quantities to be estimated from the MEADS pressure measurements include the total pressure, dynamic pressure, Mach number, angle of attack, and angle of sideslip. Secondary objectives are to estimate atmospheric winds by coupling the pressure measurements with the on-board Inertial Measurement Unit (IMU) data. This paper provides details of the algorithm development, MEADS system performance based on calibration, and uncertainty analysis for the aerodynamic and atmospheric quantities of interest. The work presented here is part of the MEDLI performance pre-flight validation and will culminate with processing flight data after Mars entry in 2012.

Adjustment of the basin-scale circulation at 26° N to variations in Gulf Stream, deep western boundary current and Ekman transports as observed by the Rapid array

Abstract: . The Rapid instrument array across the Atlantic Ocean along 26° N provides unprecedented monitoring of the basin-scale circulation. A unique feature of the Rapid array is the combination of full-depth moorings with instruments measuring temperature, salinity, pressure time series at many depths with co-located bottom pressure measurements so that dynamic pressure can be measured from surface to bottom. Bottom pressure measurements show a zonally uniform rise (and fall) of bottom pressure of 0.015 dbar on a 5 to 10 day time scale, suggesting that the Atlantic basin is filling and draining on a short time scale. After removing the zonally uniform bottom pressure fluctuations, bottom pressure variations at 4000 m depth against the western boundary compensate instantaneously for baroclinic fluctuations in the strength and structure of the deep western boundary current so there is no basin-scale mass imbalance resulting from variations in the deep western boundary current. After removing the mass compensating bottom pressure, residual bottom pressure fluctuations at the western boundary just east of the Bahamas balance variations in Gulf Stream transport. Again the compensation appears to be especially confined close to the western boundary. Thus, fluctuations in either Gulf Stream or deep western boundary current transports are compensated in a depth independent (barotropic) manner very close to the continental slope off the Bahamas. In contrast, compensation for variations in wind-driven surface Ekman transport appears to involve fluctuations in both western basin and eastern basin bottom pressures, though the bottom pressure difference fluctuations appear to be a factor of 3 too large, perhaps due to an inability to resolve small bottom pressure fluctuations after removal of larger zonal average, baroclinic, and Gulf Stream pressure components. For 4 tall moorings where time series dynamic height (geostrophic pressure) profiles can be estimated from sea surface to ocean bottom and bottom pressure can be added, there is no general correlation between surface dynamic height and bottom pressure. Dynamic height on each mooring is strongly correlated with sea surface height from satellite observations and the variability in both dynamic height and satellite sea surface height decrease sharply as the western boundary is approached.

Instability of Pressure Relief Valves in Water Pipes

Abstract: Pressure relief valves in water pipes are known to sometimes chatter when the inlet pressure slightly exceeds the set pressure. While these devices are responsible for numerous fatigue issues in process industries, there is a relatively low number of technical publications covering their performance, especially in heavy fluid applications. The present study is intended as a contribution to the understanding of pressure relief valve dynamics, taking into account fluid-structure interactions. A series of tests were performed with a water relief valve in a test rig. Adjusting the set pressure of the valve to about 30 bars, an upstream pressure varying from 20 bars to 35 bars was imposed, so that the valve opened and the water flow varied from a few m 3 /h to about 80 m 3 /h. During the tests, the pipe was equipped upstream and downstream of the valve with static pressure sensors and a flowmeter, the disk lift was measured with a laser displacement sensor, and the spring force was recorded simultaneously. Several fluctuating pressure sensors were also installed in the inlet pipe. Static instability is investigated by comparing the spring force to the hydraulic force. Dynamic instability is observed and it is shown that the resonant behavior of the disk generates an apparent negative pressure drop coefficient at some frequencies. This negative pressure drop coefficient can trigger a dynamic instability in a manner similar to the negative damping effect in leakage-flow vibrations.

Diagnosing a cooling subsystem of an engine system in response to dynamic pressure sensed in the subsystem

Abstract: A method of diagnosing a cooling subsystem of an engine system in response a parameter extracted from dynamic hydraulic pressure sensed in the cooling subsystem, and products and systems using same.

Three-dimensional numerical modeling of secondary flows in a wide curved channel

Abstract: Most natural rivers are curved channels, where the turbulent flows have a complex helical pattern, as has been extensively studied both numerically and experimentally. The helical flow structure in curved channels has an important bearing on sediment transport, riverbed evolution, and pollutant transport study. In this article, different turbulence closure schemes i.e., the mixing-length model and the k – ɛ model with different pressure solution techniques i. e., hydrostatic assumptions and dynamic pressure treatments are applied to study the helical secondary flows in an experiment curved channel. The agreements of vertically-averaged velocities between the simulated results obtained by using different turbulence models with different pressure solution techniques and the measured data are satisfactory. Their discrepancies with respect to surface elevations, superelevations and secondary flow patterns are discussed.

Measurement of Pressure Distribution from PIV Experiments

Abstract: In this study, a non-staggered grid SIMPLER pressure solution algorithm, which is able to produce correct pressure distribution directly if correct velocities are given, is proposed to solve the pressure distribution for PIV experiments. The cell face pseudo velocity required in the pressure equation is approximated by a simple linear average of the adjacent nodal pseudo velocities so that the velocity and pressure are collocated without causing the checkerboard pressure distribution problem. In addition, the proposed pressure solution algorithm has the features that upwind effects of the convective terms are considered, boundary conditions are not required, and the pressure distribution obtained can be used to correct the velocity field so that the continuity equation is satisfied. These features make the present algorithm a superior method to calculate the pressure distribution for PIV experiments. The pressure field solved is realistic and accurate. The proposed pressure equation solver is first calibrated with a two-dimensional cavity flow. It is found that the results are almost identical to the exact solution of the test flow. The algorithm is then applied to analyze a uniform flow past two side-by-side circular cylinders in a soap film channel. With the velocity and pressure distributions successfully measured, the structures of the complex shedding flow patterns are clearly manifested.

Apparatus and method for measuring small rocket engine thrust force vector in vacuum

Abstract: The invention relates to a measuring device and a method for detecting thrust vector of a tiny rocket motor used in vacuum. The device for detecting the thrust vector mainly comprises a pressure probe, a movable platform, a rotating table and a data acquisition system. The method comprises the following steps: fixing the pressure probe to the movable platform first, and then adjusting the position of the pressure probe simultaneously, so as to make an axis of the pressure probe parallel to an axis of the tiny rocket motor. When the movable platform moves at constant speed along the direction perpendicular to the axis of the tiny rocket motor, a sensor positioned in the pressure probe senses local dynamic pressure signals in jet current generated by the tiny rocket motor in real time, and the acquisition system acquires and transmits the signals to a data processing and displaying system. Through analyzing symmetry of the dynamic pressure relative to the axis of the tiny rocket motor, the method studies deflection conditions of actual thrust vector and design objective.

Test method and system of train pneumatic performance simulation test apparatus

Abstract: The invention relates to a testing method and system for a train aerodynamic performance simulation testing device, which is used for testing various performance parameters of high-speed running train model in simulation test. The testing method comprises: arranging a train-carried data collection system in the train model, which is used for dynamic pressure tests of each testing point of the train model and tests of speed of the train model; arranging a ground data collection system on ground of the track, which is used for testing ground dynamic pressure and environmental parameters when the train model passes by the ground testing points. The invention is capable of real-timely recording dynamic change process of the train and ground air pressure, and accurately testing speed of the train model, thereby realizing tests of various test parameters such as dynamic pressure, speed, and the like, required for the simulation test, and obtaining test data of real-time and accurate train and ground dynamic pressure change data.

Statistical properties of flux closure induced by solar wind dynamic pressure fronts

Abstract: [1] We present a statistical study of flux closure intervals induced by solar wind dynamic pressure fronts. We consider that a dynamic pressure front reaches the Earth when a dayside subauroral proton flash is observed in the SI2 channel of the IMAGE-FUV experiment. This pragmatic criterion selects both weak and strong pressure fronts. It is found that the preconditioning of the magnetosphere prior to the pressure pulse arrival mainly governs the magnetospheric response to a weak solar wind dynamic pressure front. This preconditioning includes the amount of open magnetic flux available in the magnetosphere prior to the pressure front arrival and the size of the magnetospheric cavity. However, in the case of a strong pressure pulse, the magnetospheric response is more sensitive to the solar wind properties characterizing the dynamic pressure front. The pressure jump is not the only one important, but also the variation of the solar wind velocity and IMF magnitude. In overall terms, we find that a strong dynamic pressure front is typically characterized by a dynamic pressure increase larger than ∼2.8 nPa that takes place on timescales of the order of a few minutes.

Computational aeroacoustic analysis of a ¼ scale g550 nose landing gear and comparison to nasa & ufl wind tunnel data

Abstract: In conjunction with the NASA-Gulfstream and Gulfstream-University of Florida wind tunnel testing of a generic nose landing gear model, Computational Aero-Acoustics research was conducted at Gulfstream using the commercial Navier-Stokes Finite Volume CFD solver STAR-CCM+. The simulation modeled the ¼ scale G550 nose landing gear mounted in the NASA Basic Aerodynamics Research Tunnel (BART) wind tunnel test section. The model was run at the 0.166 Mach Number condition on the simplified nose landing gear with the gear cavity closed. Prior to simulation execution, dynamic pressure probes were inserted onto the surface of the model at the exact locations of the dynamic pressure transducers on the nose landing gear wind tunnel model. Delayed Detached Eddy Simulation (DDES) (1) was run with a 58 million cell unstructured grid on 47 3.0 GHz quad-core processors for approximately two weeks to obtain a total of 0.05 seconds of statistically limit-cycled pressure data was processed. Results of the simulation were compared to data from the NASA BART and University of Florida anechoic wind tunnel results at both surface mounted steady and unsteady pressure transducers. The simulation showed good agreement in comparisons of power spectral density up to 5 kHz at mesh/time step dependent frequencies at all locations captured. In addition, the simulation was in somewhat good agreement with the measured mean turbulence levels at the wheel hub height and good agreement at static pressure taps located on the starboard wheel.

Full-scale shake table investigation of bridge abutment lateral earth pressure

Abstract: SUMMARY During strong seismic excitation, passive earth pressure at the abutments may provide resistance to longitudinal displacement of the bridge deck. The dynamic pressure component may also contribute to undesirable abutment movement or damage. Current uncertainty in the passive force-displacement relationship and in the dynamic response of abutment backfills continues to motivate large-scale experimentation. In this regard, a test series is conducted to measure static and dynamic lateral earth pressure on a 1.7 meter high bridge abutment wall. Built in a large soil container, the wall is displaced horizontally into the dense sand backfill, in order to record the passive force-displacement relationship. The wall-backfill system is also subjected to shake table excitation. In the conducted tests, lateral earth pressure on the wall remained close to the static value during the low to moderate shaking events (up to about 0.5g). At higher levels of input acceleration, a substantial portion of the backfill inertial force started to clearly act on the wall.

Measurement of specimen dimensions and dynamic pressure in dynamic triaxial experiments

Abstract: Novel experimental techniques are developed to measure the rapid changes in specimen dimensions during dynamic triaxial experiments. A capacitance gage is designed and constructed to measure the diameter change of the specimen inside the pressure chamber at both low and high rates. The length change is determined by a linear variable differential transformer at low rates and by Kolsky bar signals at high rates. The Kolsky bar also measures the dynamic axial stress in the specimen during the high-rate phase of an experiment. A line pressure gage records the hydrostatic pressure in the chamber. The dynamic pressure variation in the chamber during axial impact loading is detected by a manganin gage placed inside the chamber. The feasibility of this new experimental setup is demonstrated by dynamic triaxial experiments on a fine dry sand.

Magnetospheric cavity modes driven by solar wind dynamic pressure

Abstract: [1] We present results from Lyon-Fedder-Mobarry (LFM) global, three-dimensional magnetohydrodynamic (MHD) simulations of the solar wind-magnetosphere interaction. We use these simulations to investigate the role that solar wind dynamic pressure fluctuations play in the generation of magnetospheric ultra-low frequency (ULF) pulsations. The simulations presented in this study are driven with idealized solar wind input conditions. In four of the simulations, we introduce monochromatic ULF fluctuations in the upstream solar wind dynamic pressure. In the fifth simulation, we introduce a continuum of ULF frequencies in the upstream solar wind dynamic pressure fluctuations. In this numerical experiment, the idealized nature of the solar wind driving conditions allows us to study the magnetospheric response to only a fluctuating upstream dynamic pressure, while holding all other solar wind driving parameters constant. The simulation results suggest that ULF fluctuations in the solar wind dynamic pressure can drive magnetospheric ULF pulsations in the electric and magnetic fields on the dayside. Moreover, the simulation results suggest that when the driving frequency of the solar wind dynamic pressure fluctuations matches one of the natural frequencies of the magnetosphere, magnetospheric cavity modes can be energized.

Estimating engine parameters based on dynamic pressure readings

Abstract: A method and system for estimating engine parameters in a combustion engine gas exchange system based on dynamic pressure readings taken by one or more pressure sensors. According to an exemplary embodiment, the method and system may use an artificial neural network (ANN) to process the dynamic pressure readings and any additional engine conditions that may have been provided.

Protection of oil-filled transformer against explosion: Numerical simulations on a 200 MVA transformer

Abstract: Oil filled transformer explosions and their prevention are a complex industrial issue. Experimental tests showed that when an electrical fault occurs in a transformer, it generates dynamic pressure waves that propagate in the oil. Reflections of these waves on the walls build up high static pressure which transformer tanks can not withstand. Besides, a numerical tool was developed to simulate the phenomena highlighted during the tests and mainly the pressure wave propagation. It is based on a compressible two-phase flow modelling where viscous flow, electromagnetic, thermal and gravity effects are taken into account. The equations are solved using a finite volume method allowing computing complex 3D transformer geometries. Simulations of the consequence of an electrical arc occurring in a 200 MVA transformer geometry show that the static pressure increase can be prevented by a quick oil evacuation triggered by the first dynamic pressure peak generated by the electrical arc.

Experimental Investigations of Pressure Distortions on the High-Pressure Compressor Operating Behavior

Abstract: Experimental investigations of coupled total pressure inlet distortion effects on the unsteady behavior of the five-stage high-pressure compressor Rig 212 from the RB199-jet engine development have been carried out in this work. The total pressure inlet distortions were generated by two distortion generators in the intake, facilitating the combination of steady and unsteady distortion. The determination of the flowfield in the compressor inlet plane immediately in front of the first rotor showed a very complex pattern with abrupt changes in the distribution of pressures, angles, and Mach numbers. An explicit allocation of generated distortions was possible. Evidence was obtained of an interaction between distortions, even in undistorted sectors. The expected strong loss of power was seen in the compressor map similar to a suction-side throttling, meaning an inlet flow reduction with a lowering of the surge margin toward lower pressure ratios. No dependency was determined between the rotation direction of distortion and the location of the surge margin. The flow analysis in the compressor inlet plane and through the machine in the axial direction showed merely slight differences at the beginning of stall in all configurations with distortion. The type of distortion has, however, an influence on the fully developed stall. There were no indications of prestall effects when the distortion generators were used.

Experimental Pulsator Characterization for Liquid Injector Research

Abstract: The Propulsion Research Center at the University of Alabama in Huntsville (PRC) has designed and built a hydro-mechanical pulsator to simulate the effects of high frequency combustion instability (HFCI) in liquid rocket engines (LRE). The response characteristics (output pressure fluctuation, amplitude, and frequency) of the pulsator were evaluated in an atmospheric test rig with filtered de-ionized water as the primary fluid. The outlet of the pulsator was connected to a swirl injector LOX post to provide some downstream flow resistance. The pulsator control variables (primary flow bypass throttle, back pressure throttle, motor drive frequency and steady state injector pressure) were systematically varied to assess the dependence of the output flow characteristics on the control variables. For each test, the average mass flow rates of the waste water, seal water leakage, and fluid delivered through the injector were measured. Dynamic pressure was measured at the pulsator exit and the mean static pressure was measured at both the injector and at the pulsator inlets. High frequency pressure measurements show a periodic pressure pulsation with maximum peak to peak amplitude of 2% of the injector pressure when the pulsator is activated. The preliminary characterization of the pulsator was insufficient to fully characterize the pulsator; however, general trends showing the relationship between the control variables are visible in the data. The relationships between the variables show that higher order curve fits are required but the amount of data collected in this initial characterization is insufficient to generate those relationships.

A rotor blade

Abstract: Cooling within aerofoils (30, 47, 67, 87) is a requirement in order that the materials from which the aerofoil (30, 47, 67, 87) is created can remain within acceptable operational parameters. Traditionally static pressure as well as enhanced dynamic pressure impingement flows have been utilised but there are problems with regard to achieving a necessary over pressure to avoid hot gas ingestion or reduced cooling effect. It will be appreciated that fluid flows and in particular coolant fluid flows must be used most appropriately in order to maintain operational efficiency. By providing a plurality of feed apertures (41, 61, 81) which are shaped to have an entry portion (51, 71, 91) which is generally elliptical and an exit portion (52, 72, 92) it is possible to grab and turn a proportion of a feed flow (44, 64, 84) for substantially perpendicular or other angular presentation to an opposed surface of a cooling chamber (42, 62, 82) within which cooling is required.