Impingement of Under-Expanded Jets on a Flat Plate

1990 ◽  
Vol 112 (2) ◽  
pp. 179-184 ◽  
Author(s):  
J. Iwamoto
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Flat Plate ◽  
Maximum Pressure ◽  
Axially Symmetric ◽  
Symmetric Flow ◽  
Reversed Flow ◽  
Pressure Distributions ◽  
Sonic Jet ◽  
Wave Forms

When an under-expanded sonic jet impinges on a perpendicular flat plate, a shock wave forms just in front of the plate and some interesting phenomena can occur in the flow field between the shock and the plate. In this paper, experimental and numerical results on the flow pattern of this impinging jet are presented. In the experiments the flow field was visualized using shadow-photography and Mach-Zehnder interferometry. In the numerical calculations, the two-step Lax-Wendroff scheme was applied, assuming inviscid, axially symmetric flow. Some of the pressure distributions on the plate show that the maximum pressure does not occur at the center of the plate and that a region of reversed flow exists near the center of the plate.

scholarly journals Recirculation Flow and Pressure Distributions in a Rayleigh Step Bearing

2018 ◽  
Vol 2018 ◽  
pp. 1-8
Author(s):  
Feng Shen ◽  
Cheng-Jin Yan ◽  
Jian-Feng Dai ◽  
Zhao-Miao Liu
Keyword(s):  
Flow Field ◽  
Flow Characteristics ◽  
Lower Surface ◽  
Navier Stokes ◽  
Maximum Pressure ◽  
Slider Bearing ◽  
Navier Stokes Equation ◽  
Recirculation Flow ◽  
Lubrication Equation ◽  
Pressure Distributions

Flow characteristics in the Rayleigh step slider bearing with infinite width have been studied using both analytical and numerical methods. The conservation equations of mass and momentum were solved utilizing a finite volume approach and the whole flow field was simulated. More detailed information about the flow patterns and pressure distributions neglected by the Reynolds lubrication equation has been obtained, such as jumping phenomenon around a Rayleigh step, vortex structure, and shear stress distribution. The pressure distribution of the Rayleigh step bearing with optimum geometry has been numerically simulated and the results obtained agreed with the analytical solution of the classical Reynolds lubrication equation. The simulation results show that the maximum pressure of the flow field is at the step tip not on the lower surface and the increment of the strain rate from Navier-Stokes equation is approximately 49 percent greater than that from Reynolds theory at the step tip. It is also shown that the position of the maximum pressure of the lower surface is a little less than the length of the first region. These results neglected by the Reynolds lubrication equation are important for designing a bearing.

Slow viscous flow past a rotating sphere

1971 ◽  
Vol 69 (2) ◽  
pp. 333-336 ◽  
Author(s):  
K. B. Ranger
Keyword(s):  
Stokes Flow ◽  
Rotating Fluid ◽  
Axially Symmetric ◽  
Asymmetric Flow ◽  
Symmetric Flow ◽  
Reversed Flow ◽  
Linear Superposition ◽  
Rotating Sphere ◽  
Flow Past ◽  
Uniform Stream

Keller and Rubinow(l) have considered the force on a spinning sphere which is moving through an incompressible viscous fluid by employing the method of matched asymptotic expansions to describe the asymmetric flow. Childress(2) has investigated the motion of a sphere moving through a rotating fluid and calculated a correction to the drag coefficient. Brenner(3) has also obtained some general results for the drag and couple on an obstacle which is moving through the fluid. The present paper is concerned with a similar problem, namely the axially symmetric flow past a rotating sphere due to a uniform stream of infinity. It is shown that leading terms for the flow consist of a linear superposition of a primary Stokes flow past a non-rotating sphere together with an antisymmetric secondary flow in the azimuthal plane induced by the spinning sphere. For a3n2 > 6Uv, where n is the angular velocity of the sphere, U the speed of the uniform stream, and a the radius of the sphere, there is in the azimuthal plane a region of reversed flow attached to the rear portion of the sphere. The structure of the vortex is described and is shown to be confined to the rear portion of the sphere. A similar phenomenon occurs for a sphere rotating about an axis oblique to the direction of the uniform stream but the analysis will be given in a separate paper.

scholarly journals Study on Pressure Characteristics and Its Evolution Law at the Ellipsoidal End Cover Pole of Cylindrical Explosion Containment Vessels

2020 ◽  
Vol 10 (9) ◽  
pp. 3060
Author(s):  
Yunhao Hu ◽  
Wenbin Gu ◽  
Zhen Wang ◽  
Yangming Han
Keyword(s):  
Shock Wave ◽  
Aspect Ratio ◽  
Flow Field ◽  
Simulation Method ◽  
Maximum Pressure ◽  
Pressure Curve ◽  
Time Interval ◽  
Evolution Law ◽  
Scaled Distance ◽  
Secondary Shock

To explore the postposition of the maximum pressure at the pole of the ellipsoidal end cover of cylindrical explosion containment vessels and to reveal the mechanism of the load evolution, the experimental method was used to measure the pressure curve at the pole under different charges, and the numerical simulation method was used to analyze the evolution law of the explosion flow field within the end cover. The results show that the end cover pole was subjected to three types of pressure: the primary explosion wave, the secondary shock wave and the convergence wave. In addition, the pressure peaks increased in sequence. The evolution of the flow field in the end cover was affected by the amount of charge and the aspect ratio of the vessel. When the scaled distance due to a small charge increased, or when the aspect ratio of the vessel was reduced, the time interval between the convergence wave and the secondary shock wave at the end cover pole decreased gradually. When the scaled distance increased to 4.05 m·kg−1/3, the convergence wave at the pole superimposed on the secondary shock wave. As the aspect ratio of the vessel ranged from 1.75 to 2.50, the time interval between the two peaks was about 150 μs. However, if the aspect ratio was less than 1.40, the convergence wave and the secondary shock wave were fused through complex interaction.

Pressure measurements over a hemisphere-cylinder body attached with a forward facing spike

2013 ◽  
Vol 117 (1192) ◽  
pp. 639-646 ◽  
Author(s):  
R. Kalimuthu ◽  
R. C. Mehta ◽  
E. Rathakrishnan
Keyword(s):  
Shock Wave ◽  
Aerodynamic Drag ◽  
Pressure Coefficient ◽  
Angle Of Attack ◽  
Maximum Pressure ◽  
Geometrical Parameters ◽  
Pressure Measurements ◽  
Separation Region ◽  
Pressure Distributions ◽  
Oil Flow

AbstractThe present paper presents oil flow visualisations and pressure measurements over a hemisphere-cylinder body attached with a forward facing spike at Mach 6 and Reynolds number of 1·38 × 108at 0° and 5° angle-of-attack. The oil flow pictures depict the separation region in the vicinity of the spike on the hemisphere-cylinder body. The oil flow visualisations will help to locate the reattachment shock wave on the hemisphere-cylinder body and also understand the flow field behavior on the blunt-nosed spike configuration. The pressure measurements over the hemisphere-cylinder body depend on the shape and the length of the spike. The pressure distributions over the blunt-nosed body show significant influence of the angle-of-attack. The maximum pressure coefficient on the hemisphere-cylinder body is a function of the spike length, shape of the aerodisk and angle-of-attack. The windward and leeward sides pressure variations show dependence of the geometrical parameters of the spike and shape of the spike. The hemisphere and the flat-faced aerodisk cause considerable reduction of pressure leading to decrease of aerodynamic drag compared to the conical spike.

Curvature of attached shock waves in steady axially symmetric flow

1960 ◽  
Vol 7 (4) ◽  
pp. 610-616 ◽  
Author(s):  
E. Bianco ◽  
H. Cabannes ◽  
J. Kuntzmann
Keyword(s):  
Shock Wave ◽  
Shock Waves ◽  
Numerical Integration ◽  
Electronic Computer ◽  
The Body ◽  
Supersonic Stream ◽  
Axially Symmetric ◽  
Symmetric Flow ◽  
Symmetrical Body

An electronic computer has been employed to calculate the ratio between the initial radii of curvature of the attached shock wave and the body for an axially symmetrical body in a uniform supersonic stream. The results are obtained with 4 exact digits for more than 200 cases. They extend results obtained previously (Cabannes 1951) by means of numerical integration.

scholarly journals Analysis of transonic buffet using dynamic mode decomposition

2021 ◽  
Vol 62 (4) ◽  
Author(s):  
Antje Feldhusen-Hoffmann ◽  
Christian Lagemann ◽  
Simon Loosen ◽  
Pascal Meysonnat ◽  
Michael Klaas ◽  
...  
Keyword(s):  
Shock Wave ◽  
Flow Field ◽  
Acoustic Waves ◽  
Feedback Loop ◽  
Measurement Data ◽  
Dynamic Mode Decomposition ◽  
Recirculation Region ◽  
Dynamic Mode ◽  
Mode Decomposition ◽  
Transonic Buffet

AbstractThe buffet flow field around supercritical airfoils is dominated by self-sustained shock wave oscillations on the suction side of the wing. Theories assume that this unsteadiness is driven by a feedback loop of disturbances in the flow field downstream of the shock wave whose upstream propagating part is generated by acoustic waves. High-speed particle-image velocimetry measurements are performed to investigate this feedback loop in transonic buffet flow over a supercritical DRA 2303 airfoil. The freestream Mach number is $$M_{\infty } = 0.73$$ M ∞ = 0.73 , the angle of attack is $$\alpha = 3.5^{\circ }$$ α = 3 . 5 ∘ , and the chord-based Reynolds number is $${\mathrm{Re}}_{c} = 1.9\times 10^6$$ Re c = 1.9 × 10 6 . The obtained velocity fields are processed by sparsity-promoting dynamic mode decomposition to identify the dominant dynamic features contributing strongest to the buffet flow field. Two pronounced dynamic modes are found which confirm the presence of two main features of the proposed feedback loop. One mode is related to the shock wave oscillation frequency and its shape includes the movement of the shock wave and the coupled pulsation of the recirculation region downstream of the shock wave. The other pronounced mode represents the disturbances which form the downstream propagating part of the proposed feedback loop. The frequency of this mode corresponds to the frequency of the acoustic waves which are generated by these downstream traveling disturbances and which form the upstream propagating part of the proposed feedback loop. In this study, the post-processing, i.e., the DMD, is highlighted to substantiate the existence of this vortex mode. It is this vortex mode that via the Lamb vector excites the shock oscillations. The measurement data based DMD results confirm numerical findings, i.e., the dominant buffet and vortex modes are in good agreement with the feedback loop suggested by Lee. Graphic abstract

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