On Wall Effects in Cavity Flows

1984 ◽  
Vol 28 (01) ◽  
pp. 70-75
Author(s):  
C. C. Hsu
Keyword(s):  
Numerical Results ◽  
Cavity Flows ◽  
Two Dimensional ◽  
Wall Effects ◽  
Free Jet ◽  
Theoretical Predictions ◽  
Experimental Findings ◽  
Good Agreement

Simple wall correction rules for two-dimensional and nearly two-dimensional cavity flows in closed or free jet water tunnels, based on existing linearized analyses, are made. Numerical results calculated from these expressions are compared with existing experimental findings. The present theoretical predictions are, in general, in good agreement with data.

Theoretical Investigations and Numerical Evaluations of Wall Effects in Cavity Flows

1975 ◽  
Vol 97 (4) ◽  
pp. 482-491
Author(s):  
S. Popp
Keyword(s):  
Exact Solution ◽  
Infinite Series ◽  
Cavity Flows ◽  
Two Dimensional ◽  
Cavitating Flows ◽  
Wall Effects ◽  
Numerical Computations ◽  
Hodograph Method ◽  
Shaped Body ◽  
Theoretical Investigations

The wall effects for fully and partially cavitating flows are investigated for both compressible and incompressible two-dimensional jets. The exact solution for Roshko’s model in a channel with a wedge shaped body is obtained and some particular models are studied. The hodograph method as developed by S. V. Falkovitch [19] is used and the solutions are given as infinite series of Chaplygin’s functions. The exact expressions of the drag coefficients for the aforementioned configurations are also given. Numerical computations are carried out for wedges of all angles. Tables and diagrams are included.

scholarly journals MODELING OF ELASTIC-PLASTIC DEFORMATION OF ELEMENTS OF SPATIAL STRUCTURES DURING PULSE INTERACTION WITH FLUID BASED ON THE GODUNOV'S METHOD OF INCREASED ACCURACY

2019 ◽  
Vol 81 (4) ◽  
pp. 488-499
Author(s):  
Wang Cheng ◽  
Yang Tonghui ◽  
Li Wan ◽  
Tao Li ◽  
M.H. Abuziarov ◽  
...  
Keyword(s):  
Experimental Data ◽  
Shock Waves ◽  
Elastoplastic Deformation ◽  
Three Dimensional ◽  
Numerical Results ◽  
Two Dimensional ◽  
Wave Processes ◽  
Detonation Products ◽  
Comparison Of The Results ◽  
Good Agreement

The spatial problem of internal explosive loading of an elastoplastic cylindrical container filled with water in Eulerian - Lagrangian variables using multigrid algorithms is considered. A defining system of three-dimensional equations of the dynamics of gas, fluid, and elastoplastic medium is presented. For numerical modeling, a modification of S.K. Godunov scheme of the increased accuracy for both detonation products and liquids, and elastoplastic container is used. At the moving contact boundaries “detonation products - liquid”, “liquid - deformable body”, the exact solution of the Riemann's problem is used. A time dependent model is used to describe the propagation of steady-state detonation wave through an explosive from an initiation region. In both cases, the initiation of detonation occurs at the center of the charge. Two problems have been solved: the first task for the aisymmetric position of the charge, the second for the charge shifted relative to the axis of symmetry. In the first task, the processes are two-dimensional axisymmetric in nature, in the second task, the processes are essentially three-dimensional. A comparison is made of the results of calculations of the first problem using a three-dimensional method with a solution using a previously developed two-dimensional axisymmetric method and experimental data. Good agreement is observed between the numerical results for the maximum velocities and circumferential strains obtained by various methods and experimental data. There is good agreement between the numerical results obtained by various methods and the known experimental data. Comparison of the results of solving the first and second problems shows a significant effect of the position of the charge on the wave processes in the liquid, the processes of loading the container and its elastoplastic deformation. The dynamic behavior of a gas bubble with detonation products is analyzed. A significant deviation of the bubble shape from the spherical one, caused by the action of shock waves reflected from the structure, is shown. Comparison of the results of solving the first and second problems showed a significant effect of the charge position on wave processes in a liquid, the processes of loading a container and its elastoplastic deformation. In particular, in the second problem, shock waves of higher amplitude are observed in the liquid when reflected from the walls of the container.

scholarly journals Development of a new empirical formula for prediction of triple point path

Shock Waves ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 677-686 ◽  
Author(s):  
W. Xiao ◽  
M. Andrae ◽  
N. Gebbeken
Keyword(s):  
Triple Point ◽  
Empirical Formula ◽  
Numerical Results ◽  
Two Dimensional ◽  
Fluid Density ◽  
Arbitrary Lagrangian Eulerian ◽  
Eulerian Formulation ◽  
Wide Range ◽  
Nodal Coordinates ◽  
Good Agreement

Abstract This paper develops a new empirical formula for the prediction of the triple point path in irregular shock reflection cases. Numerical simulations using a two-dimensional axisymmetric multi-material arbitrary Lagrangian–Eulerian formulation are employed to obtain the data of fluid density. Using the data of fluid density and nodal coordinates, the gradients of fluid density are determined and then used to generate numerical schlieren images. Based on these images, the triple point paths are derived and compared with the models of the Unified Facilities Criteria (UFC) and Natural Resources Defense Council (NRDC) as well as two models from the open literature. It is found that the numerically derived triple point paths are in good agreement with those predicted by a recently published model in the open literature for the typical ground range of shock wave propagation of up to 6 m. Considering the whole distance range, it is found that the agreement of different models of the triple point path with the numerical ones depends on the considered blast scenario, i.e., the scaled charge height. For small-scaled charge heights, the model of the UFC and the recently published model in the open literature are in better agreement with the numerical results than the other two models, whereas the NRDC model has the best agreement with the numerical results for large-scaled charge heights. Based on the numerical results, a new empirical formula is proposed for the prediction of the triple point path, which is valid for a wide range of the scaled charge heights from 0.5 to 3.5 m/kg1/3 and scaled ground distances up to 15 m/kg1/3.

Two-dimensional viscous gravity currents flowing over a deep porous medium

2001 ◽  
Vol 440 ◽  
pp. 359-380 ◽  
Author(s):  
JAMES M. ACTON ◽  
HERBERT E. HUPPERT ◽  
M. GRAE WORSTER
Keyword(s):  
Porous Medium ◽  
Numerical Solutions ◽  
Gravity Current ◽  
Constant Volume ◽  
Two Dimensional ◽  
Theoretical Predictions ◽  
Self Similar ◽  
Coefficient Of Viscosity ◽  
Good Agreement

The spreading of a two-dimensional, viscous gravity current propagating over and draining into a deep porous substrate is considered both theoretically and experimentally. We first determine analytically the rate of drainage of a one-dimensional layer of fluid into a porous bed and find that the theoretical predictions for the downward rate of migration of the fluid front are in excellent agreement with our laboratory experiments. The experiments suggest a rapid and simple technique for the determination of the permeability of a porous medium. We then combine the relationships for the drainage of liquid from the current through the underlying medium with a formalism for its forward motion driven by the pressure gradient arising from the slope of its free surface. For the situation in which the volume of fluid V fed to the current increases at a rate proportional to t3, where t is the time since its initiation, the shape of the current takes a self-similar form for all time and its length is proportional to t2. When the volume increases less rapidly, in particular for a constant volume, the front of the gravity current comes to rest in finite time as the effects of fluid drainage into the underlying porous medium become dominant. In this case, the runout length is independent of the coefficient of viscosity of the current, which sets the time scale of the motion. We present numerical solutions of the governing partial differential equations for the constant-volume case and find good agreement with our experimental data obtained from the flow of glycerine over a deep layer of spherical beads in air.

TAMING CHAOS IN A DRIVEN JOSEPHSON JUNCTION

2001 ◽  
Vol 11 (07) ◽  
pp. 1897-1909 ◽  
Author(s):  
R. CHACÓN ◽  
F. PALMERO ◽  
F. BALIBREA
Keyword(s):  
Josephson Junction ◽  
Phase Difference ◽  
Initial Phase ◽  
Chaotic Dynamics ◽  
Numerical Results ◽  
Initial Phase Difference ◽  
Theoretical Predictions ◽  
Melnikov Analysis ◽  
Analytical Expressions ◽  
Good Agreement

We present analytical and numerical results concerning the inhibition of chaos in a single driven Josephson junction by means of an additional weak resonant perturbation. From Melnikov analysis, we theoretically find parameter-space regions, associated with the chaos-suppressing perturbation, where chaotic states can be suppressed. In particular, we test analytical expressions for the intervals of initial phase difference between the two excitations for which chaotic dynamics can be eliminated. All the theoretical predictions are in overall good agreement with numerical results obtained by simulation.

Pressure Measurements on Flapped Hydrofoils in Cavity Flows and Wake Flows

1967 ◽  
Vol 11 (03) ◽  
pp. 170-189
Author(s):  
M. C. Meijer
Keyword(s):  
Wall Effect ◽  
Cavity Flows ◽  
Pressure Measurements ◽  
Viscous Effect ◽  
Tunnel Wall ◽  
Experimental Procedure ◽  
Wake Flows ◽  
Theoretical Predictions ◽  
Theory And Experiments ◽  
Good Agreement

The purpose of the present experiments is to obtain detailed information about the flow field, such as the pressure distribution, at the surface of a flapped hydrofoil in full cavity or wake flows. The model and the experimental procedure are described. The experimental results obtained have been used to compare with the theoretical predictions, to investigate the tunnel wall effect and to estimate the viscous effect at a sharp corner. Anempirical method for correcting the tunnel wall effect is developed here, the validity of which is supported by tests with models of three different sizes. An appreciable Viscous effect has been found near the hinge of a deflected flap. Except for this effect, the theory and experiments are found to be in good agreement.

On the Laminar Two-Dimensional Free Jet of an Incompressible Pseudoplastic Fluid

1972 ◽  
Vol 39 (4) ◽  
pp. 1162-1164 ◽  
Author(s):  
C. Atkinson
Keyword(s):  
Flow Behavior ◽  
Closed Form Solution ◽  
Form Solution ◽  
Numerical Results ◽  
Two Dimensional ◽  
Pseudoplastic Fluid ◽  
Flow Behavior Index ◽  
Free Jet ◽  
Boundary Layer Equations ◽  
Behavior Index

A closed-form solution is obtained to boundary-layer equations given by Lemieux and Unny [1] for the free outflow of a non-Newtonian pseudoplastic fluid from a two-dimensional orifice into a mass of the same fluid. Results deduced from this solution are compared with numerical results given in [1]. The analytical solution given here contradicts some of these numerical results when the flow behavior index of the fluid is less than or equal to a half.

Numerical Study on Three-Dimensional Wall Effects of Flat Micro Nozzle

2011 ◽  
Vol 339 ◽  
pp. 276-282
Author(s):  
Jun Jie Tong ◽  
Ji Wen Cen ◽  
Jin Liang Xu
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Numerical Results ◽  
Two Dimensional ◽  
Wall Effects ◽  
Micro Nozzle

The FLUENT6.1 software is applied to simulate the supersonic flow in micro convergent-divergent nozzle which is fabricated from flat silicon wafers. The simulation is complemented by parallel computing steady 2-D and 3-D Navier-stokes equations to study the three-dimensional wall effects on temperature and velocity inside the micro nozzle. Also the performances of fluent mass coefficients and thrust force efficiencies are studied. It is observed by the study that three-dimensional wall effects are not negligible in flat micro nozzle. The velocity of fluid in three-dimensional nozzle is less than the corresponding velocity of fluid in two-dimensional nozzle significantly, while the temperature of fluid in three-dimensional nozzle is much higher than the corresponding temperature of fluid in two-dimensional nozzle. The mass flow rate and thrust at the exit of 2-D nozzle are greater than the corresponding mass flow rate and thrust at the exit of three-dimensional. With the throat Renaults being increased, the corresponding differences between two-dimensional numerical results and three-dimensional numerical results decreased accordingly. Two-dimensional numerical results can not correctly predict the actual mass flow rate and thrust at the exit of micro nozzle.

Steady long slender droplets in two-dimensional straining motion

1979 ◽  
Vol 91 (3) ◽  
pp. 401-414 ◽  
Author(s):  
E. J. Hinch ◽  
A. Acrivos
Keyword(s):  
Cross Section ◽  
Experimental Results ◽  
Recent Analysis ◽  
Two Dimensional ◽  
Axisymmetric Case ◽  
Hyperbolic Flow ◽  
Theoretical Criterion ◽  
Theoretical Predictions ◽  
The Cross ◽  
Good Agreement

The recent analysis by Acrivos & Lo (1978) concerning the breakup of a long slender droplet in an axisymmetric straining motion is extended to the case of a two-dimensional hyperbolic flow. It is found that, although the cross-section of the droplet becomes significantly non-circular, the theoretical criterion for breakup is effectively the same as in the axisymmetric case. The theoretical predictions are in good agreement with the available experimental results.

scholarly journals Experimental studies of supercavitating flow about simple two-dimensional bodies in a jet

1959 ◽  
Vol 5 (3) ◽  
pp. 337-354 ◽  
Author(s):  
Edward Silberman
Keyword(s):  
Linear Theory ◽  
Experimental Studies ◽  
Cavitation Number ◽  
Two Dimensional ◽  
University Of Minnesota ◽  
Flat Plates ◽  
Force Coefficients ◽  
Free Jet ◽  
Fluid Theory ◽  
Good Agreement

A two-dimensional free-jet water tunnel developed at the St Anthony Falls Hydraulic Laboratory of the University of Minnesota is described briefly. Results of experimental measurements on a two-dimensional cup, symmetrical wedges, inclined flat plates, and a circular cylinder in the tunnel are given.Measured force coefficients at zero cavitation number are in good agreement with theory. Shapes of the cavities were computed for one of the wedges and for one of the plates at zero cavitation number; the observed shapes are also in good agreement with the theory.For non-zero cavitation numbers, theoretical results for force coefficients were available for comparison in only two cases. For one of these, the cup, agreement between theory and experiment was good up to a cavitation number of about 0.5. For the other, a symmetrical wedge, experimental results were compared with a linear theory with good agreement for cavitation numbers between about 0.1 and 0.3. In the case of the wedge, measured cavity lengths were somewhat shorter than predicted by the linear theory. All other comparisons with theory at non-zero cavitation number had to be made with the theory as developed for infinite fluid. The experimental force coefficients were less than predicted by infinite-fluid theory, but tended to approach the theoretical values as the cavitation number increased. A similar tendency marked the comparison between the experimental data and data taken by others in closed tunnels.

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