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Showing papers on "Dynamic pressure published in 1981"


Patent
03 Aug 1981
TL;DR: In this paper, a pneumatic control circuit connected the source of pressurized gas to a first chamber of a dynamic pressure wave appliance, and a valve sealing the inflated sleeve discontinues the inflation of the sleeve when the pressure therein reaches a third predetermined level.
Abstract: A source of pressurized gas is attached to a dynamic pressure wave appliance. The pneumatic control circuit connects the source of pressurized gas to a first chamber of the appliance. When the pressure in the first chamber reaches a first predetermined level, a valve seals the first chamber and connects the source so as to inflate a second chamber about the first. When the pressure in the second chamber reaches a second predetermined level, a valve permits the first chamber to deflate while continuing to connect the second chamber for inflation. A valve for sealing the inflated sleeve discontinues the inflation of the sleeve when the pressure therein reaches a third predetermined level. The sequence of operation of the pneumatic control circuit will cause a suitable dynamic pressure wave appliance to apply a pressure to a human or animal extremity which begins at the most distant end and travels up the extremity in the nature of a pressure wave.

60 citations


Journal ArticleDOI
TL;DR: In this article, the Bernoulli equation of fluid mechanics is used to analyze the change of the internal pressure of a building caused by the sudden opening of a window or door under the action of wind.
Abstract: The change of the internal pressure of a building caused by the sudden opening of a window or door under the action of wind is analyzed using the Bernoulli equation of fluid mechanics. The problem is treated at several levels of sophistication, from the simplest quasi-steady isothermal incompressible solution to the most complex solution assuming unsteady isentropic compressible flow with due regards to the inertia effect. Following the break of a window or door by wind, the internal pressure reaches the external pressure at the opening rather rapidly. After the internal pressure has reached the external pressure, there is an overshoot and subsequent oscillation of the internal pressure, in spite of the constancy of the external pressure under a steady wind. The results are compared to solutions obtained from the Helmholtz resonator model of acoustics.

58 citations


Patent
03 Aug 1981
TL;DR: In this article, a transducer is provided to generate a signal representative of the pressure within a second chamber of the appliance, and a comparator is responsive to the predetermined pressure level signals.
Abstract: The electronic circuit includes switch means responsive to the pressure within a first chamber of a dynamic pressure wave appliance for generating an enabling signal when a predetermined pressure level in the first chamber has been reached. A transducer is provided to generate a signal representative of the pressure within a second chamber of the appliance. The electronic circuit includes means for generating a signal representing a first predetermined pressure level and a second predetermined pressure level in the second chamber when the enabling signal is generated. A comparator is responsive to the predetermined pressure level signals and the transducer signal for generating control signals to a solenoid. The solenoid is connected to appropriate valves for regulating the pneumatic control circuit. The electronic control circuit will cause a dynamic pressure wave appliance to apply a pressure to a human or animal extremity which begins at the most distant end and travels up the extremity in the nature of a pressure wave.

33 citations


Journal ArticleDOI
TL;DR: In this paper, a methodology centered around the forced longitudinal wave (FLW) motor is developed to investigate dynamic responses of rocket motors, and a linear analysis was developed to study propellant pressure and velocity-coupled responses using dynamic pressure measurements at several locations in a motor.
Abstract: A methodology centered around the forced longitudinal wave (FLW) motor is being developed to investigate dynamic responses of rocket motors. The FLW motor establishes periodic longitudinal pressure and velocity oscillations in solid propellant rocket chambers. A linear analysis was developed to study propellant pressureand velocity-coupled responses using dynamic pressure measurements at several locations in a motor. The analysis uses pressure amplitude and phase measurements. Variations in the propellant reponses are shown to produce measurable changes in the calculated oscillating pressures with velocity-coupled responses showing the greatest promise for determination from experimental data. Experimentally deduced velocity-coupled response functions are examined over a frequency range centered around the chamber fundamental mode for a range of interior flowfields and chamber pressures for 86%AP-14%HTPB propellants.

19 citations


Journal ArticleDOI
TL;DR: In this article, extensive spectral measurements of the wall pressure field for flow Mach numbers in the range 0·2-0·5 are presented, and regions where higher order modes are detectable are identified.

15 citations


Patent
24 Jul 1981
TL;DR: In this article, a hydraulic circuit for a so-called feathering control of a variable displacement pump is presented, in which displacement of the variable displacement pumps is controlled to a minimum when every actuator in a system is not in operation.
Abstract: A hydraulic circuit for a so called feathering control of a variable displacement pump in which displacement of the variable displacement pump is controlled to a minimum when every actuator in a system is not in operation thereby keeping a power loss to a minimum. The hydraulic circuit includes a jet flow sensor for detecting a dynamic pressure of fluid. The jet flow sensor is disposed in a circuit for connecting a system pressure line to a reservoir and is adapted to convert static pressure of the fluid to dynamic pressure thereof. This detected dynamic pressure is introduced into a servo mechanism for the variable displacement pump for effecting feathering control.

9 citations



Patent
21 Jan 1981
TL;DR: In this paper, the authors propose a method for air conditioning control where multiple pressure conditions are added algebraically with independent modular diaphragm systems and adjust upstream dampers in response to the algebraic difference between static pressure and velocity pressure.
Abstract: Method and apparatus for air conditioning control where multiple pressure conditions are added algebraically with independent modular diaphragm systems. The method provides automatic balance of pressure and velocity conditions by adjusting upstream dampers in response to the algebraic difference between static pressure and velocity pressure.

6 citations



Patent
23 Jan 1981
TL;DR: In this paper, a three-hole yaw probe or similar sensing means which is immersed in the stream to provide measurements of both static pressure differential and velocity pressure is presented. But the measurement of the velocity pressure measurements or the square root thereof are exhibited on a first digital display (28) permitting the operator to monitor the measurements as they are taken.
Abstract: A device which can determine either the velocity pressure or the velocity of a flowing gas or air stream and averages same over a predetermined period of time is disclosed. The device utilizes a three-hole yaw probe or similar sensing means which is immersed in the stream to provide measurements of both static pressure differential and velocity pressure. The device includes a null threshold detector (14) which permits the processing of velocity pressure measurements only when the static pressure differential is within a pre-set range thus insuring the proper alignment of the probe or other sensing means in the stream. A square root extractor (20) and switching means (22) are also provided permitting the measurement and averaging of the square root of the velocity pressure measurement, i.e., velocity of the stream, by the device. The velocity pressure measurements or the square root thereof are exhibited on a first digital display (28) permitting the operator to monitor the measurements as they are taken. The measurements are subsequently averaged over a predetermined period of time by an arithmetic processor (18) and the resulting average is exhibited on a second digital display (30).

5 citations


Journal ArticleDOI
TL;DR: In this paper, a generalized two-point boundary problem methodology is applied to the design and flight analysis of a two-stage air-breathing launch vehicle, and the optimal system fuel consumption and staging Mach number are found to vary little with changes in the inequality constraints due to substantial geometry and trajectory adjustments.
Abstract: A generalized two-point boundary problem methodology, similar to techniques used in deterministic optimal control studies, is applied to the design and flight analysis of a two-stage air-breathing launch vehicle. Simultaneous consideration is given to configuration and trajectory by treating geometry, dynamic discontinuities, and time-dependent flight variables all as controls to be optimized with respect to a single mathematical performance measure. While minimizing fuel consumption, inequality constraints are applied to dynamic pressure and specific force. The optimal system fuel consumption and staging Mach number are found to vary little with changes in the inequality constraints due to substantial geometry and trajectory adjustments. Staging, from an air-breathing first stage to a rocket-powered second stage, consistently occurs near Mach 3.5. The dynamic pressure bound has its most pronounced effects on vehicle geometry, particularly the air-breathing propulsion inlet area, and on the first-stage altitude profile. The specific force has its greatest influence on the second-stage thrust history.

Patent
20 Aug 1981
TL;DR: In this paper, a transducer is used to pick up the resonant frequency of a piston held in place in a cylinder by longitudinal taut strings, which is linearly dependant on the tensioning of the strings.
Abstract: Static pressure (8) is applied to one side and dynamic (7) to the other of a piston (2) held in place in a cylinder (1) by longitudinal taut strings (3,4). Each string has an electromagnet type oscillator (9,10) associated, and a transducer (11,12) for picking up its resonant frequency. A comparator (15) establishes the frequency-difference which is a measure of the speed. The piston may be sealed to the cylinder, using an elastic substance (17) such as silicone-rubber. High accuracy is achieved since the pressure difference can be directly converted to digital signals. The resonance frequency is linearly dependant on the tensioning of the strings. Interference effects such as temp. changes are equalised by the opposite sides.


01 Nov 1981
TL;DR: In this article, a high aspect ratio supercritical wing with oscillating control surfaces is described and a semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures.
Abstract: A high aspect ratio supercritical wing with oscillating control surfaces is described. The semispan wing model was instrumented with 252 static orifices and 164 in situ dynamic pressure gases for studying the effects of control surface position and sinusoidal motion on steady and unsteady pressures. Data from the present test (this is the second in a series of tests on this model) were obtained in the Langley Transonic Dynamics Tunnel at Mach numbers of 0.60 and 0.78 and are presented in tabular form.


Patent
07 Mar 1981
TL;DR: In this paper, a check valve equipped in parallel with the flow control orifice was used to secure valve operation regardless of leakage at the sliding surface of a pressure receiving piece in an opening/closing valve device.
Abstract: PURPOSE:To secure valve operation regardless of leakage at the sliding surface of a pressure receiving piece in an opening/closing valve device in which the pressure in the flow-in chamber is to act on both sides of the pressure receiving piece, by providing a pressure relief valve in parallel with the flow control orifice. CONSTITUTION:While valve 27 is closed, the pressure in a flow-in chamber 2 is introduced to both chambers 12a,12b of a pressure receiving piece housing 12 through No.1 pressure introducing hole 18 and No.2 pressure introducing passage 22 and there no pressure difference is produced, thereby closing of the valve 27 is conducted with the dynamic pressure in flow-in chamber 2 which acts on the back of the valve element 5. When the valve 27 is opened, the pressure in the flow-in chamber 2 is lowered by an orifice 23 and the pressure in the downstream chamber 12b becomes low, and thus the pressure receiving piece 16 is lifted up to open the valve. Because a check valve 25 equipped in parallel with the flow control orifice 24 opens at this time, the pressure in the chamber 12b will not rise up even through the sliding surface of the pressure receiving piece allows minor leakage. The valve element 5 can be thus operated securely.

01 Aug 1981
TL;DR: In this paper, the authors analyzed the dynamic response and structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence and provided guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays.
Abstract: Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

Journal ArticleDOI
TL;DR: In this article, separate and combined wind tunnel and vibration shaker tests were conducted on two structural panels representative of the Shuttle Orbiter in the NASA/LaRC 8 ft Transonic Pressure Tunnel to determine the effects of combined loads on the Thermal Protection System (TPS).
Abstract: Separate and combined wind tunnel and vibration shaker tests were conducted on two structural panels representative of the Shuttle Orbiter in the NASA/LaRC 8 ft Transonic Pressure Tunnel to determine the effects of combined loads on the Thermal Protection System (TPS). Objectives of this test were to provide a combined full scale load environment and realistic time history of the dynamic pressures and responses and Mach numbers (through transonic) to these panels. Panels were selected from locations where interactive load sources such as aerodynamic shock waves, turbulent boundary layers, strut‐induced vorticity, and substrate deformation combined to provide high bonding loads between the TPS and the Orbiter structure. Test panels were instrumented with static and dynamic pressure gauges, accelerometers, deflectometers, strain gauges, schlieren and high speed photography, and instrumentation necessary to determine SIP/structure interface loads. Two test specimens of each Orbiter panel were utilized. The f...

Journal ArticleDOI
TL;DR: In this paper, the influence of internal pressure and static loads on the dynamic characteristics of cable-reinforced inflatable caps is studied numerically, where the structure is modelled as a three-dimensional cable reinforced network with the action of the membrane neglected except for transmitting pressure load to the cables.
Abstract: The influence of internal pressure and static loads on the dynamic characteristics of cable-reinforced inflatable caps is studied numerically. The structure is modelled as a three-dimensional cable-reinforced network with the action of the membrane neglected except for transmitting pressure load to the cables. For relatively small static loads, including snow and dead weight, the natural frequencies are approximately proportional to the square root of the internal pressure. The dynamic response of the structure under the action of static wind load differs considerably from that without such loading. The static wind-type load causes the natural frequencies to vary, particulary to decrease the fundamental frequency.

Patent
21 Feb 1981
TL;DR: In this article, the authors propose to provide buffers as vibration proof means in fluid passages, which are connected to cylinders containing pistons which support a weighing table, to block pressure waves transmitted from pressure reception pipes.
Abstract: PURPOSE:To assure the stability of a pointer, by providing buffers as vibration- proof means in fluid passages, which are connected to cylinders containing pistons which support a weighing table, to block pressure waves transmitted from pressure reception pipes. CONSTITUTION:Buffers 9 shaped as stepped rods are provided in fluid passages 3A-3D to prevent impulsive pressure waves from being transmitted from pressure receiving sections 1 to a load meter 7 through pressure reception pipes 4 and a connector 3. Each buffer 9 comprises a part 9A of outside diameter smaller than the diameter of a hole 3a1 and another part 9B screwed in a tapped hole 3a2. A thin passage 9b, which extends in a radial direction and communicates with another passage 9a, is opened in the peripheral surface of the part 9A. The hole 3a1 and tapped hole 3a2 of the fluid passage 3A communicate with each other only through the passages 9a, 9b. According to this constitution, strong impulsive pressure waves transmitted from the interior of the pressure reception pipe 4 are reflected on the end face of the part 9A so that the pressure waves do not enter into the passage 9b. As a result, the dynamic pressure waves are not transmitted to the interior of a pipe 5 for the meter.

ReportDOI
01 Feb 1981
TL;DR: In this article, wind tunnel tests of different configurations of the XM445 fuze were conducted at the Naval Surface Weapons Center in November 1979, with measurements of temperature and pressure provided new information on conditions in the fuze.
Abstract: : As part of the development of the fluidic power supply of the XM445 fuze, wind tunnel tests of different configurations of the power supply were conducted at the Naval Surface Weapons Center in November 1979. Power supply performance and pressure and temperature measurements within the fuze were recorded at Mach 1.5 and Mach 5 for a range of pressures. Success or failure of any given configuration was based on degree of sensitivity at low pressure and ability to operate at high pressure and temperature. Measurements of temperature and pressure provided new information on conditions in the fuze.

Journal Article
TL;DR: In this paper, the inlet pressure vibration in the induction system consists of two main waves, which can be distinguished clearly and explained by acoustic theory, and the relation between the design factors and these waves is calculated by using acoustic theory.
Abstract: Volumetric efficiency and inlet pressure vibration of a four cylinder engine with air-surge-tank was investigated. It was found that the inlet pressure vibration in the induction system consists of two main waves, which can be distinguished clearly and explained by acoustic theory. One has a short period which is determined by factors of the induction system from the air purge-tank to the intake valve, the other has a relatively long period which is determined by overall design factors of the induction system. According to the numerical calculation, it was clarified that the volumetric efficiency is strongly influenced by the pressure in the short period before the intake valve closed. Therefore, how the design factors of the induction system are affecting the volumetric efficiency of the four cylinder engine with air-surge-tank can be shown by the following procedure. First, the mean pressure of two main waves in the short period before the intake valve closed are examined. It the pressure is positive value, the volumetric efficiency is improved by the wave. Second, the relation between the design factors and these waves is calculated by using acoustic theory.