A Note on Choking Cavitation Flow Past Bluff Bodies

1992 ◽  
Vol 114 (3) ◽  
pp. 439-442 ◽  
Author(s):  
A. S. Ramamurthy ◽  
R. Balachandar
Keyword(s):  
Pressure Distribution ◽  
Cavitation Number ◽  
Experimental Results ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Interference Effects ◽  
Cavitation Flow ◽  
Prismatic Body ◽  
Flow Past

A model is developed to predict the choking cavitation number for sharp edged bluff bodies subject to wall interference effects. The fact that the forebody pressure distribution under cavitating conditions essentially resembles the values obtained in noncavitating flows is made use of in the development of the model. The model is verified using experimental results from present and previous studies for a specific case of choking flow past a two-dimensional prismatic body.

Blockage Effects on Cavitation Inception Characteristics of Bluff Bodies

1991 ◽  
Vol 205 (6) ◽  
pp. 415-419 ◽  
Author(s):  
R Balachandar ◽  
A S Ramamurthy
Keyword(s):  
Bluff Body ◽  
Experimental Results ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Interference Effects ◽  
Cavitation Inception ◽  
Proposed Model

The study deals with the prediction of cavitation inception in the wake of two-dimensional bluff bodies subject to wall interference effects. Corrections are included in the model to account for flow entrainment effects and loss of circulation in the vortices shed from the bluff body. Experimental results are also presented to verify the proposed model over a range of blockages.

Hydrodynamic Trends for Preliminary Design of Fully Cavitating Hydrofoil Sections

1977 ◽  
Vol 14 (01) ◽  
pp. 70-85
Author(s):  
Blaine R. Parkin ◽  
Robert F. Davis ◽  
Joseph Fernandez
Keyword(s):  
Pressure Distribution ◽  
Lift Coefficient ◽  
Flow Theory ◽  
Cavity Flow ◽  
Cavitation Number ◽  
Viscous Drag ◽  
Preliminary Design ◽  
Two Dimensional ◽  
Cavity Thickness ◽  
Cavitating Hydrofoil

The object of this numerical study is to consider possible hydrodynamic trends for use in trade-off studies for the preliminary design of fully cavitating hydrofoil sections. Hydrodynamic data are obtained from inverse calculations which are based upon two-dimensional linearized cavity-flow theory. Supplementary data are also calculated from the direct problem of linearized cavity-flow theory in order to show off-design performance trends and to assess the effects of cavity-foil interference on the operating range of selected profiles. For the inverse calculations one specifies design values of the lift coefficient, cavitation number, and cavity thickness at the trailing edge, as well as the shape of the pressure distribution on the wetted surface of the hydrofoil section. In accordance with this specification, the ordinates of the profile wetted surface and upper-cavity contour are calculated, together with values of drag coefficient, moment coefficient, and attack angle at the design point. The paper summarizes the results of a parametric study of the effects of design cavitation number, lift coefficient, cavity thickness, and pressure distribution shape upon hydrofoil section performance and geometry. Three-dimensional wing effects, viscous drag, and the effects of structural design criteria are all outside the scope of the study. Results pertaining to steady two-dimensional cavity flows of an ideal incompressible fluid past a rigid hydrofoil section are presented.

Inverse Methods in the Linearized Theory of Fully Cavitating Hydrofoils

1964 ◽  
Vol 86 (4) ◽  
pp. 641-654 ◽  
Author(s):  
B. R. Parkin ◽  
R. S. Grote
Keyword(s):  
Inverse Problem ◽  
Pressure Distribution ◽  
Cavitation Number ◽  
Inverse Methods ◽  
Two Dimensional ◽  
Physical Constraints ◽  
Two Dimensional Flow ◽  
Linearized Theory ◽  
Profile Design ◽  
Major Emphasis

Theoretical and numerical procedures are given for the design of fully cavitating hydrofoils in a steady two-dimensional flow. The only boundary in the flow is that provided by the hydrofoil and its cavity. The cavity is always assumed to spring from the nose and trailing edge of the profile. The methods used are those of linearized inverse airfoil theory, in which one prescribes the pressure distribution on the wetted surface of the profile and then calculates its shape. The theory at zero cavitation number is considered anew in order to highlight the physical constraints involved in this inverse problem. However, major emphasis is given to basic procedures for profile design at nonzero or zero cavitation numbers. Optimum hydrofoil design is discussed from an engineering viewpoint.

An approximate theory for incompressible viscous flow past two-dimensional bluff bodies in the intermediate Reynolds number regime O(1) < Re < O(102)

1976 ◽  
Vol 77 (1) ◽  
pp. 129-152 ◽  
Author(s):  
Sheldon Weinbaum ◽  
Michael S. Kolansky ◽  
Michael J. Gluckman ◽  
Robert Pfeffer
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Pressure Gradient ◽  
Boundary Layer Theory ◽  
Navier Stokes ◽  
Bluff Bodies ◽  
Approximate Theory ◽  
Two Dimensional ◽  
First Order ◽  
Flow Past

A new approximate theory is proposed for treating the flow past smoothly contoured two-dimensional bluff bodies in the intermediate Reynolds number rangeO(1) <Re< 0(102), where the displacement effect of the thick viscous layer near the surface of the body is large and a steady laminar wake is present. The theory is based on a new pressure hypothesis which enables one to take account of the displacement interaction and centrifugal effects in thick viscous layers using conventional first-order boundary-layer equations. The basic question asked is how the wall pressure gradient in ordinary boundary -layer theory must be modified if the pressure gradient along the displacement surface using the Prandtl pressure hypothesis is to be equal to the pressure gradient along this surface using a higher-order approximation to the Navier-Stokes equation in which centrifugal forces are considered. The inclusion of the normal pressure field with displacement interaction is shown to be equivalent to stretching the streamwise body co-ordinate in first-order boundary-layer theory such that the streamwise pressure gradient as a function of distance along the original and displacement body surfaces are equal.While the new theory is of a non-rigorous nature, it yields results for the location of separation and detailed surface pressure and vorticity distribution which are in remarkably good agreement with the large body of available numerical Navier-Stokes solutions. A novel feature of the new boundary-value problem is the development of a simple but accurate approximate method for determining the inviscid flow past an arbitrary two-dimensional displacement body with its wake.

Effects of Corner Cutoffs on Flow Past Two Square Cylinders in a Tandem Arrangement

2012 ◽  
Author(s):  
Y. T. Krishne Gowda ◽  
H. V. Ravindra ◽  
C. K. Vikram
Keyword(s):  
Reynolds Number ◽  
Pressure Distribution ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Lift Coefficient ◽  
Two Dimensional ◽  
Square Cylinder ◽  
Tandem Arrangement ◽  
Square Cylinders ◽  
Flow Past

Flow past the two square cylinders with and without corner modification in a tandem arrangement has been simulated using a CFD code FLUENT. A Reynolds number of 100 and pitch to perimeter ratios (PPR) of 2,4 and 6 are considered for the investigation. The flow is assumed to be two dimensional unsteady and incompressible. The obtained results are presented in the form of streamlines, pressure distribution, monitored velocity, lift coefficient and Strouhal number. Results indicate, in case of chamfered and rounded corners, there is decrease in the wake width and thereby the lift values. For the square cylinders of same perimeters with and without corner modification, the size of the eddy and the monitored velocity in between the square cylinders increases with increase in PPR. Frequency of vortex shedding is same in between the cylinders and in the downstream of the cylinder. Frequency of vortex shedding decreases with the introduction of second cylinder either in the upstream or downstream of the first cylinder. The lift coefficient of square cylinder with corner modification decreases but Strouhal number increases when compared with a square cylinder without corner modification.

Computation of flow past single two-dimensional bluff bodies

1990 ◽  
Author(s):  
WOE-CHUL PARK ◽  
HIROSHI HIGUCHI
Keyword(s):  
Bluff Bodies ◽  
Two Dimensional ◽  
Flow Past
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