Showing papers on "Dynamic pressure published in 1970"

Numerical Model for Wave Pressure Distributions

Abstract: A mathematical model based on the wave-equation which governs the propagation of small amplitude pressure disturbances through a fluid is used to compute the temporal and spatial variation of impact or shock pressure against vertical wall subjected to breaking wave action. A separate development using conservation of momentum principles results in an equation for the maximum pressure in terms of both breaker characteristics and the time required for the pressure in terms of both breaker characteristics and the time required for the pressure to reach its maximum value. Experiments indicate the existence of two types of impact pressure. Significant impact pressures act over large areas of a structure simultaneously while ordinary impact pressures are more localized. The role of air in decreasing the magnitude of the maximum pressure and in retarding the propagation of the pressure disturbance appears important as the model and data compare favorably when c = 400 fps. This reduction in the sonic velocity through a mixture of air and water will occur with only a 1% volume of entrained air.

Fluidic flow sensing method and apparatus

Abstract: Fluidic flow sensing techniques are disclosed which permit sensitive flow measurements over a wider range of flow rates than was heretofore possible. In one embodiment a jet of working fluid, directed parallel to the sensed flow, is modulated by viscous interaction with the sensed flow, thereby changing the downstream dynamic pressure of the jet as a function of the sensed flow. In a second embodiment a jet of working fluid is directed angularly with respect to the sensed flow, producing jet deflection which is monitored as a differential pressure across a pair of downstream receivers. A negative feedback circuit, including a high gain amplifier fed by the differential pressure, controls the jet supply pressure to maintain a differential pressure null across the receivers, thereby rendering the jet supply pressure a function of the sensed flow.

Sinusoidal pressure calibrator

Abstract: Disclosed is a dynamic pressure calibrator for calibrating particularly piezoelectric pressure transducers for relatively high and rapid sinusoidal pressure variations. The calibrator comprises a housing on which are mounted both a standard and a test transducer. A seismic mass of known weight within the housing is vibrated when the device is placed on a shaker table and acts through a piston and a hydraulic oil reservoir in the housing to simultaneously apply equal pressure forces to the transducers so their outputs can be compared. An accelerometer senses seismic mass acceleration and the transducers are preferably preloaded through the oil.

Ink bleed tester

Abstract: A device for testing printed fibrous material, such as paper napkins and the like for resistance to ink bleed. The device includes a base and a support on the base for receiving the material to be tested while pressure is applied to the material, when it is stationary, for determining bleed resistance of the fibrous test material as it is undergoing static pressure. Means are also provided for pulling adjacent material through the receiving means while pressure is being applied to the test material, so as to determine the resistance of the test material to dynamic pressure or rubbing.

Flutter of buckled plates at zero dynamic pressure

Abstract: Buckled plates flutter at zero dynamic pressure, considering initial plate imperfections, including aerodynamic damping in quasi-steady supersonic approximation

Technique for inducing controlled steady-state and dynamic inlet pressure disturbances for jet engine tests

Abstract: Secondary air injection achieving momentum interchanges to induce controlled steady state dynamic pressure disturbances for jet engine tests

Second Order Analysis Of Dynamic Pressure Profiles, Using MeasuredHorizontal Wave Flow Velocity Component

Abstract: There is an increasing need for pressure field knowledge under wave flows due to its importance in coastal structure design. Several studies have been conducted in such a way as to accurately learn the behavior of those pressure fields in trying to define reliable formulae for design purposes, describing with a better degree of detail the maximum values achieved as well as the stochastic aspects of the wave action. This article intends to present the evolution of pressure fields under the action of incident regular waves, as a function of its phase and relative depth, comparing them with a linear and a second order wave theory. These wave fields were obtained in an indirect way, through the horizontal wave flow velocity component. The measurements were carried out in the unidirectional wave tank of the Faculty of Engineering of the University of Porto. The wave tank was 4,8 m wide, 24,5 m long and has a maximum water depth of 0,40 m near the test section. Some profiles of the dynamic pressure are represented for each relative water depth (zld) and for different wave phases. The results obtained with the horizontal velocity component were compared with the results given by the theories and with the related values through the measured mean water elevations. The agreement between the different values is reasonable, especially for some wave phases. The differences could be explained by secondary or higher order effects.

Flow and Pressure of Noncohesive Granular Materials in Deep Bin (Part 2)

Abstract: In preceding papers, we reported some measurements of lateral pressures acting on the inside wall ot full-sized grain bins. We showed in these works that the pressures which occured during discharge are much greater than those of initial static conditions.The present report mentioned about both the lateral pressure measurements on a full-sized deep bin and the flow patterns of granular materials during discharge from model silo.According to these tests, the principal results are obtained as follows.(1) The fundamental flow patterns which occure during discharge from silo are one of the very important causes for the dynamic over-pressures.(2) There are three different characteristics of this dynamic pressure of materials and these phenomena relate to the fundamental flow patterns.(3) Basing on these flow patterns, we present an approximate theoretical solution of these dynamic overpressures acting on the walls of deep bin.

Dynamic analysis of XB-70-1 inlet pressure fluctuations during takeoff and prior to a compressor stall at Mach 2.5

Abstract: Inlet pressure fluctuation in XB-70 aircraft during takeoff and prior to compressor stall at Mach 2.5

In‐Flight Exterior Pressure Fluctuation Measurements on the Boeing Model 737 Airplane

Abstract: The in‐flight fluctuating pressures were measured with a microphone array, which consisted of seven flush mounted 14‐in. B & K microphones. The flight‐test measurements were carried out at the two locations (28 and 67 ft from nose) in a level flight at Mach numbers of 0.78 and 0.45 and also when stationary, on ground, at MTO power (on the aft array only). Various aerodynamic parameters were calculated. The PSD measurements for the forward position compared favorably with the laboratory measurements. Root‐mean‐square pressure fluctuation was found to be 3.53 times shear stress at the wall or 0.0056 times free‐stream dynamic pressure. Wide‐band space‐time correlation measurements indicated slightly higher decay rate, which was attributed to angle between fuselage axis and flow direction in a level flight and also to the effects of fuselage curvature. Over‐all convection velocities ranged between 0.5 and 0.8 times true air speed. The measurements at the aft location showed higher noise levels compared to the...

Jet velocity augmentation apparatus

Abstract: A jet velocity augmentation scheme employs a pulsed fluid source of relatively incompressible fluid which produces at least two fluid jets which are caused to impact on one another with the leading faces of the fluid jets at a relatively small angle, for instance

Velocity pressure effect on sprinkler system discharge

Abstract: After conducting a series of sprinkler discharge tests, the authors concluded that the use of velocity pressure in sprinkler system calculations will give a false picture of the ability of the system.

Wake Properties Behind a Flared Cylindrical Forebody and Aerodynamic Characteristics of Several Flexible Aerodynamic Decelerators at Mach Numbers from 1.75 to 4.75

Abstract: : A test was conducted to determine the flow field properties in the wake of a strut-mounted cylindrical forebody with and without base bleed and to determine aerodynamic performance of two types of parachutes. The wake was surveyed from two to eight forebody diameters aft of the base. Parachute separation distance was remotely varied from four to nine forebody diameters aft of the base. Data were obtained at Mach numbers from 1.75 to 4.75 at a nominal free-stream dynamic pressure of 80 psf. Base bleed reduced the local wake Mach number and dynamic pressure behind the forebody at all X/D locations for Z/D = zero. The addition of webs to the Supersonic X parachute, in general, decreased the parachute dynamics at Mach numbers greater than three.