Showing papers on "Dynamic pressure published in 1972"

The Pressure Perturbation and the Numerical Modeling of a Cloud

Abstract: The adaptation of the deep convection equations of Ogura and Phillips to moist convection results in an implicit relationship between temperature, potential temperature, pressure, and saturation vapor pressure. Typically, the pressure is treated as a known function of height to eliminate this condition. The effect of this approximation is investigated by numerically integrating the primitive equations in two-dimensional Cartesian coordinates. The model includes precipitation, and the equations are integrated for the life cycle of a strong cumulus cell. The result indicates that the non-dimensional pressure perturbation is notably an order smaller than scale analysis indicates it might be and that the deviation from the environmental pressure can be ignored in determining the saturation vapor pressure. This is partly because the pressure diagnostic equation acts to smooth out the pressure distribution.

Instrumentation for measuring static pressure fluctuations within the atmospheric boundary layer

Abstract: An instrument is described which is capable of making Eulerian measurements of microscale fluctuations in the static pressure when it is placed within the turbulent flow of the lower atmospheric boundary layer. The sampling ports are located on an accurately shaped streamlined circular disc; dynamic pressure changes at these ports, due to the flow fluctuations, are small when compared to the static pressure changes. Wind tunnel tests and anin situ test show that the instrument can sample the amplitudes and phases of fluctuations in the static pressure to better than ± 20% and to about ± 5 °, respectively.

Explosion detection and suppression method and apparatus

Abstract: In a coal mine passage, a plurality of stored bags which can be rapidly inflated with an inflating medium having a combustion suppressing agent to form a barrier to the propagation of a combustion reaction of a fuel-air mixture, such as a mixture of coal dust and/or methane and air. To detect an incipient propagating combustion reaction, there is a radiation sensor, a static pressure sensor and a dynamic pressure sensor. There is a data analysis computer comprising a discriminator which determines a condition where radiation is above a certain predetermined level, and static and dynamic pressure are below a predetermined level within an initial short time period (e.g. 0.15 seconds) of sensing such increased radiation. When such a condition exists, the discriminating means arms an activating means which inflates the barrier bags in response to a predetermined level of increase of any one of the following five values: static pressure, dynamic pressure, rate of dynamic air pressure increase, rate of static pressure increase, and rate of radiation increase. Thus the apparatus discriminates between an actual condition of a possible rapidly propagating combustion reaction and such other disturbances as a stationary flame, electrical spark or a blast wave that do not result in such reaction. By initially containing the combustion suppressing medium in an inflatable, a more effective barrier is formed.

Distortion and Turbulence Interaction - A Method for Evaluating Engine Inlet Compatibility

Abstract: This paper discusses the method of evaluating supersonic-aircraft inlet steady-state pressure defects and random pressure fluctuations (turbulence) used for the purpose of establishing inlet engine compatibility for the TF30 engine. This technique has evolved from TF30/F-111 compatibility studies over the last several years and has resulted in a unique yet practical method of determining engine-inlet compatibility associated with applications of the TF30 series. A review is made of the development of a distortion factor for steady-state inlet pressure distortion, its basic inability to handle the dynamic pressure variations, the evaluation of this turbulence, and development of a technique to evaluate turbulence effect on engine stability margin.

An experimental assessment of the added mass of some plates vibrating in water

Abstract: A reservoir of water is contained by a concrete valley block, a ferrocement wall and a steel plate. Both wall and plate contain an array of pressure transducer sockets (Figures 1 and 2). Using the M.A.M.A.1 equipment pure modes of vibration are excited. Frequency and mode shape are measured with the reservoir empty. When the reservoir is full hydrodynamic pressure is also measured. These hydrodynamic pressures are compared with Chopra's2 two-dimensional, series solution, which includes compressibility of water, and with two- and three-dimensional finite element solutions of Laplace's equation, which do not include compressibility. Chopra's solution is unsatisfactory for modes which contain a vertical node line. The best agreement between experimental and theoretical hydrodynamic pressure is obtained when the latter is obtained from three-dimensional solutions of Laplace's equations, indicating that compressibility does not play a significant rǒle. This conclusion is supported by agreement between experimental frequencies (reservoir full) and those calculated using added mass obtained from the Laplace solution. Similar conclusions were reached from tests on a floating steel plate, suspended in the surface of the reservoir by a soft spring. Here, dynamic pressure measurements were not made, reliance being placed on agreement between calculated and measured frequencies and mode shapes.

Decomposition of a Liquid Jet Injected Normal to a Supersonic Air Stream

Abstract: : A systematic experimental study of the breakup of a liquid jet injected normal to a supersonic airstream was carried out. Included were the effect of liquid properties, jet flow rate, dynamic pressure ratio, Mach number (2.4 to 4.0), boundary layer thickness upstream of the jet, orifice size and shape, and level of jet back pressure relative to liquid vapor pressure. High-frequency, axially-propagating waves are studied as the principal decomposition mechanism, since in their instability they grow along the curved jet to a point where a large clump of fluid detaches from the cohesive jet at a wave-trough. The wave process was studied extensively by use of high-speed photographic techniques. (Author)

Experimental evaluation of the aerodynamic damping of skin panels at low supersonic Mach numbers.

Abstract: The aerodynamic damping of the first three vibration modes of a rectangular panel exposed to an attached turbulent boundary layer has been measured over the Mach number range of 1.10 to 1.40. Data showing that aerodynamic damping is a strong function of Mach number, dynamic pressure, mode shape, and boundary layer thickness are presented. At low supersonic Mach numbers, aerodynamic damping was found to be 20 to 100 times as large as common values of structural damping. Means of calculating aerodynamic damping, including effects of the boundary layer profile, are discussed. Calculated aerodynamic damping is compared with experimental data.

Dynamic Pressure of Ice on Hydraulic Structures

Abstract: : The article contains a critical survey of certain published formulas and the derivation of new formulas for finding the value of dynamic ice pressure on the vertical and inclined starlings and walls, a comparison of calculated values and recommendations, as well as those observed in the experiment and in nature. (Author)

Calibration of Some Subsonic Wind Tunnel Inserts for Two-Dimensional Airfoil Experiments

Abstract: : Parallel wall inserts were installed in the Naval Ship Research and Development Center 8 x 10-foot subsonic tunnel to create a 3 x 8 foot channel to serve as a high flow quality two-dimensional test section for high lift testing. A detailed flow survey indicated good flow uniformity, negligible angularity, a thin wall boundary layer at the model station, and a pronounced effect of trailing edge wall flaps on controlling test section dynamic pressure. A pair of two-dimensional airfoil sections tested in the facility displayed good agreement with reference data in lift and pressure distribution, but some disagreement in wake rake drag data. The strong influence of model lift on test section dynamic pressure measurement was noted, and a measurement technique was developed which was independent of the static pressure field propogating from the airfoil.

Rocket ascent G-limited moment-balanced optimization program (RAGMOP)

Abstract: This document describes the RAGMOP (Rocket Ascent G-limited Momentbalanced Optimization Program) computer program for parametric ascent trajectory optimization RAGMOP computes optimum polynomial-form attitude control histories, launch azimuth, engine burn-time, and gross liftoff weight for space shuttle type vehicles using a search-accelerated, gradient projection parameter optimization technique The trajectory model available in RAGMOP includes a rotating oblate earth model, the option of input wind tables, discrete and/or continuous throttling for the purposes of limiting the thrust acceleration and/or the maximum dynamic pressure, limitation of the structural load indicators (the product of dynamic pressure with angle-of-attack and sideslip angle), and a wide selection of intermediate and terminal equality constraints

Dynamic response of high-frequency pressure transducers to large amplitude sinusoidal pressure oscillations

Abstract: Dynamic response characteristics of six currently used dynamic pressure transducers were investigated by using a large-amplitude sinusoidal-pressure generator. Frequencies between 1 and 15 kilohertz with corresponding peak-to-peak pressure-oscillation amplitudes ranging between 73 and 8 percent of bias pressure and bias pressures between 15 and 300 psia were utilized. Amplitude-ratio data as functions of frequency and pressure level are given for all transducers. The generator design and performance and associated instrumentation are described.

Forward-Speed Effects on Peripheral-Jet Ground Support Systems

Abstract: This paper presents a theory for the effect of forward speed on a two-dimensional peripheral-jet ground-effect support. New analytical models are proposed for the flow at the peripheral-jet nozzle exit and the cross flow underneath the support. Results are presented for the lower-surface pressure distribution as well as the lift and ideal pumping power. The theory is supported by a comprehensive experimental study conducted with a two-dimensional model in a moving-ground wind tunnel. The model was externally fed and had a flat bottom. At low subcritical speeds, the effect of forward speed is found to be adverse in the absence of upper-surface lift. The theory predicts the freestream dynamic pressure to be less than the average cushion pressure for this model at critical speeds. At high subcritical speeds performance improved such that lift-power requirements at critical speeds are 20-30% below those at hover. Throughout the subcritical speed regime there is general agreement between theory and experiment. Although not considered in the present work the theory can be extended for a limited range above critical speed and to three-dimensional supports.

Pressure Losses in Simple Dump Combustors

Abstract: : Volume limited missiles require a particularly exacting form of component integration. In the integral rocket ramjet (IRR) system the propellant, for the solid rocket booster, is cast directly into the same volume that is used for the ramjet combustor. This study is directed to a better understanding of the pressure losses in dump combustors. Attendant to this study was an effort to simplify methods of predicting compressible flow losses. Application of the incompressible pressure loss factors and equations to compressible problems can lead to serious errors at Mach numbers above 0.3. During this study an equation was derived to predict compressible pressure losses. This equation expresses the pressure loss as a function of the Mach number and a pressure loss factor which is independent of Mach number. Subsequently it was found that the compressible pressure loss factor, called N sub D the dissipation number, was numerically equal to the incompressible pressure loss factor, K sub t, for any given fluid system. The incompressible parameter is basically a function of geometry and Reynolds number and there exists a wealth of data relating to it. Two basic dump combustor designs were selected for testing because of their possible use in missile propulsion. The first was a coaxial circular inlet model, the second a dual side-mounted rectangular inlet model. The measured dissipation numbers were compared to the predicted incompressible parameters and found to be encouragingly similar. The results of this study show, on a preliminary basis, that it may be possible to use the existing incompressible data to predict compressible pressure losses.

Apparatus and method for balancing fluid distribution systems

Abstract: 1283676 Measuring fluid-flow ALLIED THERMAL CORP 19 April 1971 [24 Feb 1970] 22003/71 Heading G1R In apparatus for measuring and controlling the gas flow in a fluid distribution system a housing 4 in the system contains a damper unit 14 and a screen 70 and is provided downstream of the damper 14 with a dynamic pressure indicator 50, connected to a differencial pressure gauge 64, and a static pressure indicator 72, also connected to gauge 64 and downstream of the screen 70 and the arrangement is such that the gauge 64 will give an indication of the difference between the dynamic and static pressures. The damper vanes 18 are adjustable between the full and dotted line position, Fig.3, by rod 24 moving a bracket 28, attached to a slotted and slidable plate 32 engaging nubs 23 on vanes 18. The apparatus is insertable into an air distribution system, Fig. 5 (not shown), to effect equal air distribution to various parts of the system.

A Theoretical Study of Fluid Dynamic Energy Separation

Abstract: : Three classes of energy separation techniques are analyzed and compared; steady flow, employed by the Ranque-Hilsch vortex tube (RHT); nonsteady flow, used by the dynamic pressure exchanger divider (DPE); and cryptosteady flow, used in the Foa energy separator (FES). The RHT is analyzed first to establish upper bound performance curves which are then compared with the best known experimental data; these exhibit performance generally in the range of one-half to two-thirds of theoretical. The discussion of the DPE is based on experimental data presented in the literature. The data reveal excellent low pressure ratio performance. However, cold fraction for maximum temperature drop decreases rapidly with increasing pressure ratio. The FES is analyzed to provide equations defining the dependence of performance on salient design and operational parameters. Additionally, several output flow collection effects are identified and analyzed. Comparison of the three devices indicates that the FES substantially outperforms tHE RHT at all pressure ratios and the DPE at all but the lowest pressure ratios.

Model Support Effects on Aerodynamic and Wake Characteristics of Large Angle Cones

Abstract: The Langley Research Center of NASA has conducted an experimental program on a 140° cone model in an attempt to gain more insight into such factors as Reynolds number effects and sting-support interference in wind-tunnel tests of decelerator-shaped vehicles. In addition, an effort was made to assess the cause of experimentally observed asymmetric wake patterns behind blunt bodies, often attributed to model and/or support asymetrics, by utilizing an existing tunnel-spanning support and a single wall-mounted support in tests with the same model. The tests were performed in the Langley Unitary Plan wind tunnel. The 140° cone force tests were performed at M = 1.50 and 2.00 through an angle-of-attack range from about —3° to 13° at Reynolds numbers from 1.74 x 10 to 1.44 x 15 based on model diameter, D. Sting support diameters varied from 0.125 d/D to 0.500 d\D. The wake survey tests behind a 120° cone were performed at a Mach number of 1.60, at angles-ofattack of 0° and 5°, and at a Reynolds number of 6.60 x 10. Additional force data on the 140° cone at M= 1.50 and 2.0 and wake survey data on the 120° cone at different x/D distance may be found in Ref. 1. The results of the force tests are presented in coefficient form about the body axis with the moment reference located at the model base. These coefficients are nondimensionalized with base area and base diameter of the cone. Base pressure tubes were located at the centroid of area on the base of the cone at 90° intervals and also in the balance cavity. Chamber and base pressures were measured on all sting-diameter configurations; however, the axial-force coefficients are for total values and have not been corrected for base pressure. In the wake survey measurements, two support systems were used with the 120° cone. One support system was mounted in such a manner as to span the tunnel test section. The second support system was a single-strut, mounted on the wall of the tunnel. The wake survey results are presented as the ratio of local dynamic pressure to that in freestream. Local pressures were measured by means of a multitube rake. The rake was mounted in a vertical position in the tunnel and could be moved laterally and longitudinally in the test section.