Experimental Pressure Distributions Research Articles

Base pressure in laminar supersonic flow

An asymptotic description is proposed for supersonic laminar flow over a wedge or a backward-facing step, for large Reynolds number and for a base or step height which is small compared with the boundary-layer length. The analysis is carried out for adiabatic wall conditions and a viscosity coefficient proportional to temperature. In a particular limit corresponding to a very thick boundary layer, a similarity law is obtained for the base pressure is obtained which shows the dependence on the parameters explicitly and which permits good agreement with experiment. This latter result is based on an inviscid-flow approximation for the corner expansion and for reattachment, with viscous forces important primarily in a thin sublayer about the dividing streamline. A prediction of the pressure distribution at reattachment is given and the result is compared with experimental pressure distributions.

Theoretical and Experimental Pressure Distribution in Supersonic Domain for an Inherently Compensated Circular Thrust Bearing

The authors present an equation describing the pressure distribution in the supersonic domain, for a lightly loaded bearing, including a friction factor as an explicit term. This paper contains also a few experimental curves showing the effect of rounding the edge of an inherently compensated orifice.

Closure to “Discussions of ‘Theoretical and Experimental Pressure Distribution in Supersonic Domain for an Inherently Compensated Circular Thrust Bearing’” (1973, ASME J. Lubr. Technol., 95, p. 221)

Closure to “Discussions of ‘Theoretical and Experimental Pressure Distribution in Supersonic Domain for an Inherently Compensated Circular Thrust Bearing’” (1973, ASME J. Lubr. Technol., 95, p. 221)

Inverse method of designing two-dimensional transonic airfoil sections.

The approximate compressible theory of two-dimensional airfoil sections at transonic speeds is obtained by means of the method of integral relations and quasi-linearization. The theory is an inverse method in which airfoil sections are obtained from prescribed velocity distributions which are assumed to be shock free at design Mach numbers. In order to decrease the number of strips necessary to keep the accuracy of results, the singularity of equations at stagnation points is removed analytically and the remaining regular parts of equations are transformed into a two-point boundary value problem of a system of nonlinear ordinary differential equations by means of the method of integral relations; and these equations are integrated through using quasi-linearization and the Runge-Kutta-Gill numerical method. Application of quasi-linearization admits the use of as many strips as one wishes and the accuracy of results can be improved without limit. An iterative cycle is set up to make the resulting profiles close when the pressure distributions are arbitrarily prescribed. Examples of airfoil sections designed with a four strip method and an experimental pressure distribution are presented. The rate of convergence of quasi-linearization is shown to be high.

Flow Fields in a Two-Dimensional Diffuser With Extraction of Fluid on the Diverging Walls

A theory is developed to describe the inviscid core in two-dimensional unstalled diffusers with suction (extraction) on the diverging walls. Experimental wall static pressure distributions and streamline patterns agree well with those predicted theoretically. Under appropriate extraction conditions, a stagnation region is located downstream of the diverging wall extraction station. Experimental verification of the streamline patterns and of the location of this stagnation region was achieved via hydrogen bubble visualization. In addition, the possible stall conditions, which result if improper extraction is employed, are described qualitatively.

The Impingement of a Uniform, Axisymmetric, Supersonic Jet on a Perpendicular Flat Plate

SummaryThe impingement region produced by directing a uniform, axisymmetric, supersonic jet of air normally onto a large, flat plate has been investigated experimentally and theoretically for four jets in the Mach number range 1·64 to 2·77. A qualitative theoretical description of the flow in the neighbourhood of the sonic line is given. A single-strip version of the method of Polynomial Approximation and Integral Relations (PIR) is applied to the flow, using two alternative methods of determining the centre-line shock height. The PIR predictions are compared to experimental shock shapes and pressure distributions. It is found that a PIR method in which the sonic line is assumed to intersect the shock at the jet edge leads to very good agreement with experiment at the higher jet Mach numbers, but accuracy is much reduced at the lower Mach numbers, the shock height being in error by about 62 per cent at a jet Mach number of 1·64. A change in flow pattern at small nozzle-to-plate distances is reported.

Turbulent HeatmTransfer Measurements on a Blunt Cone at Angle of Attack

Turbulent heat-transfer rates measured on the conical surface of a blunt 9° half-angle cone in a MO, = 10.6 nitrogen flow at various angles of attack are presented. The measurements were made at a nominal Rem/ft of 12(10)6 at angles of attack of a = 0°, 2.5°, 5°, 10°, 15°, and 20°. The boundary layer was tripped in order to attain turbulent flow over the model. Detailed distributions of the heat-transfer rate and surface pressure were obtained in the circumferential (A<£ = 22.5°) as well as the axial directions (S/RN < 10). Turbulent heat-transfer rates computed along inviscid surface streamlines, wherein the streamline pattern was determined utilizing the experimental pressure distributions, are compared to the data. Good agreement is obtained in the regions where the assumption of neglecting the effect of entropy swallowing utilized in the analysis is valid. The turbulent heat-transfer formulation proposed by Vaglio-Laurin as being applicable in three-dimensional flows is shown to be a good approximation for these test conditions. The influence of streamline spreading is demonstrated as well as the relative accuracy of equivalent cone techniques. The results of numerical calculations of the surface pressure are compared to the data and good agreement is achieved, except in regions where viscous-inviscid interactions become important.

Laminar boundary layer on a cone at incidence in supersonic flow

Results of three-dimensional boundary-layer calculations for a pointed cone and comparisons with experimental data are presented. Using a similarity transformation, the explicit dependence of the equations on axial position is removed. A further transformation is made to remove a singularity at the leeward symmetry plane. The resulting equations, in two independent variables, are then solved with an implicit finite difference technique by marching around the cone from the windward to the leeward symmetry plane. A technique for computing the edge properties from an experimental pressure distribution is developed. The comparisons with experimental data demonstrate that the theory provides an adequate representation of the viscous flow over most of the cone surface, although the physical model breaks down near the leeward symmetry plane.

翼型の翼型抗力の計算法

Methods for calculating the profile drag of airfoils in incompressible and compressible flows are presented respectively. Both methods are constructed by the current. boundany layer theories which have reasonable accuracy. In these method ghe calculated or experimental pressure distributions on airfoils must be given in advance.Profile drag has been calculated by these methods for several airfoils in both incompressible flow and subcritical subsonic flow at various lift coefficients and Reynolds numbers. Comparison of the results with available experimental data show good agreement.

The fluid mechanics of the ureter from a lubrication theory point of view

The function of a healthy ureter is analyzed in terms of a fluid-mechanical model. To the extent that the Reynolds number is of the order of one, the fundamental equations are shown to reduce to those of the theory of lubrication. It is found that from the point of view of the pressure variation with time (the urometrogram) the important part of the peristaltic wave is the constricting part. For this reason this part of the wave is represented with an algebraic expression of the form h ∼ xn making it possible to find closed form solutions. Using Fourier analysis in defining the complete wave shape of the ureter it was also possible to obtain numerical solutions. For both cases it is shown that there is good agreement between the theoretical and experimental pressure distributions, this not being the case for sinusoidal wave shapes. An approximate equation for the flux is developed and a universal relation is presented connecting the maximum pressure, flux and kinematic behaviour of the ureter.

Local heat and mass transfer from rigid spheres

Sh I = 00447 Re0.78Sco’33 (3) 200-200000. The experimental data of Xenakis was also included with the two sets of data for naphthalene in this part of the study. There are two questions with respect to the analysis resulting in equations (2) and (3). 1. The Xenakis data represent supercritical flow regime conditions, therefore, these data should not be included in a correlation with subcritical flow data. The naphthalene data represent a Reynolds number range of 136-25 350. 2. Correlations for Sh 2 are observed to result in a more linear relationship with Reynolds number than does Sh on a log-log plot. Another objection is that the analysis resulting in equation (1) is based upon an experimental pressure distribution for spheres at a Reynolds number of approximately 200000. This represents the transcritical flow regime and would not be applicable to the subcritical flow data. Galloway and Sage [4] analyzed the available experimental data for local heat and mass transfer from spheres and developed correlations for the prediction of local coefficients as a function of Reynolds number, intensity of free stream turbulence, and polar angle. These correlations are based upon data in the Prandtl number range of 04-68 [3, 5-81 and the Schmidt number range of 0.7-1210 [l, 9-111 and for Reynolds numbers less than 150 000. The correlations are of the form :

Mass transfer in a nonuniform impinging jet: Part II. Boundary layer flow‐mass transfer

AbstractExact solutions of the boundary layer equations were used to calculate the local mass transfer coefficients for an impinging jet with a parabolic velocity distribution. Boundary conditions were obtained from an inviscid flow solution and also from experimental pressure distributions. Experimental data for the air/naphthalene system were in good agreement with theoretical results. Mass transfer from the impingement surface was independent of nozzle height in the range 0.5 to 12 nozzle radii. For lower nozzle heights the effect of the constriction of flow between the nozzle and the surface led to increased transfer rates near the nozzle wall; data followed the predicted behavior.

Mass transfer in a nonuniform impinging jet: Part I. Stagnation flow‐velocity and pressure distribution

AbstractA theoretical solution for the impingement flow of a jet with a parabolic velocity distribution is given. Viscous generation and diffusion of vorticity in the jet were neglected. Experimental velocity and pressure distributions measured in an impinging jet of air originating with Poiseuille flow compare well with theory, thus justifying the assumption of inviscid flow. Pressure distributions on the deflecting surface were independent of nozzle height in the range 1 to 12 nozzle radii. For lower nozzle heights the effect of the constriction of flow between the nozzle and the surface followed the predicted behavior.

Circular Channel Magnetohydrodynamic Experiments in a Transverse Magnetic Field

Experimental static pressure distributions and velocity profiles are reported for mercury flow through circular pipes in a transverse magnetic field. Both laminar and turbulent flows were investigated.

Statistical analysis of inhomogeneities in experimental pressure distributions on circular casings of underground structures

Statistical analysis of inhomogeneities in experimental pressure distributions on circular casings of underground structures

Aerodynamic loading on a two-dimensional airfoil during dynamic stall.

A general theory is developed for the unsteady aerodynamic loading on an airfoil during dynamic stall. The dynamic stall process is represented by the shedding of vorticity from the vicinity of the airfoil leading edge. The theory is subsequently applied to the prediction of the stall-induced airloading on an airfoil experiencing a sudden onset of flow and on an airfoil performing oscillatory pitching motion. Satisfactory agreement between theoretical and experimental pressure distributions, forces and moments, and vortex trajectories is demonstrated.

Some Experiments at Low Speed on Compressor Cascades

Some results of recent work on low-speed cascade tunnels are described. Preliminary investigations, directed toward the analysis and improvement of the airflow and testing techniques, revealed that, when porous sidewall suction was employed, almost all change in axial velocity occurred within the blade row. Variation of axial velocity ratio, aspect ratio, Reynolds number, and turbulence level for one particular cascade facilitated an explanation of differences between the results of early British and American cascade tests. More recently, work has involved cascade tests on an analytically derived cascade. Good agreement was obtained between theoretical and experimental pressure distributions and profile boundary layers.

Analysis of an Externally Pressurized Thrust Collar Gas-Bearing with Multiple Supply Holes

An externally pressurized thrust gas-bearing with multiple supply holes, which has no recess, is investigated by use of the complex potential theory. Using a series of complex pontential functions, which satisfies the boundary conditions, the load capacity of this bearing can be calculated theoretically, and the volume rate of flow as well. Experimental pressure distributions coincide very well with theoretical ones especially for the case with low supply pressure and small bearing clearance. Experiments are also made to investigate theoretically the load capacity, yielding good agreement between experiments and theory, with consideration of secondary effects due to the compressibility of the fluid and pressure loss for the acceleration of the fluid at supply holes and for the change of the flow velocity profiles, whose effects are estimated by assuming a flow pattern.

Shock-Induced Separation of a Laminar Boundary Layer in Supersonic Flow Past a Convex Corner

SummaryThis paper presents a theoretical investigation of the interactions which occur when a laminar boundary layer on a flat surface encounters an expansive corner followed by a shock or other compressive agency. The method consists basically of two equations; the first relates deflections in the external streamlines to pressure changes and the second relates pressure changes to thickening or thinning of the boundary layer. For simplicity it is assumed that the pressure changes and streamline deflections are small.A comparison is made with the only available experimental results, under conditions which are far outside the range of applicability of the theory. In these circumstances the agreement between the predicted and experimental pressure distributions is reasonable.

Heat Transfer and Flow Characteristics Over a Lenticular Aerodynamic Body

Experimental heat transfer and pressure distributions have been obtained, at a Mach number of 3.97, for the forward portion of a low drag lenticular aerodynamic body at zero angle of attack. It is shown that the experimental results can be predicted within engineering accuracy by using a simple strip analysis. Further, an interesting similarity for both the heat transfer coefficients and static pressures has been observed in the region of investigation .