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.

A Numerical Optimization Technique Applied to the Design of Two-Dimensional Cavitating Hydrofoil Sections

1996 ◽  
Vol 40 (01) ◽  
pp. 28-38
Author(s):  
Shigenori Mishima ◽  
Spyros A. Kinnas
Keyword(s):  
Numerical Optimization ◽  
Cavity Length ◽  
Optimization Technique ◽  
Cavitation Number ◽  
Quadratic Functions ◽  
Two Dimensional ◽  
Systematic Design ◽  
Hydrodynamic Analysis ◽  
Total Drag ◽  
Cavitating Hydrofoil

A numerical nonlinear optimization technique is applied to the systematic design of two-dimensional partially or supercavitating hydrofoil sections. The design objective is to minimize the hydrofoil drag for given lift and cavitation number. The hydrodynamic analysis of the cavitating hydrofoil is performed in nonlinear theory, via a low-order potential-based panel method. The effects of viscosity are taken into account via a uniform friction coefficient applied on the wetted foil surface. The total drag, lift, cavitation number, and other quantities involved in the imposed constraints, are expressed in terms of quadratic functions of the main parameters of the hydrofoil geometry, angle of attack, and the cavity length. The optimization is based on the method of multipliers by coupling the Lagrange multiplier terms and the penalty function terms. The robustness and convergence of the method are extensively investigated, and the results are compared with those from applying other design methods.

An Extended Linearized Inverse Theory for Fully Cavitating Hydrofoil Section Design

1979 ◽  
Vol 23 (04) ◽  
pp. 260-271
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Design Theory ◽  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Cavitation Number ◽  
Inverse Theory ◽  
Cavity Surface ◽  
Moment Coefficient ◽  
Section Design ◽  
Cavity Thickness

A new design theory for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper reviews and completes the basic theory, which leads to a parametric design technique. In the resulting design procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profilelesgn, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The chief new feature of the third design procedure is that the designer can now prescribe two points on the cavity surface instead of one as heretofore. Although the designer must observe certain constraints when he specifies these two values of cavity thickness, the new procedure is still found to be more general and more flexible than design procedures studied previously.

Hydrodynamic Trends from a Generalized Design Procedure for Fully Cavitating Hydrofoil Sections

1979 ◽  
Vol 23 (04) ◽  
pp. 272-283
Author(s):  
Blaine R. Parkin ◽  
Joe Fernandez
Keyword(s):  
Parametric Design ◽  
Lift Coefficient ◽  
Design Procedure ◽  
Feasibility Studies ◽  
Cavitation Number ◽  
Hydrodynamic Performance ◽  
Cavity Surface ◽  
Cavity Flows ◽  
Moment Coefficient ◽  
Cavity Thickness

An extended design procedure for fully cavitating hydrofoils is based upon a linearized inverse theory of two-dimensional cavity flows at arbitrary cavitation number. The cavity surfaces are assumed to originate at the leading and trailing edges of the wetted surface. This paper completes the basic theory and gives detailed examples obtained from the resulting parametric design technique. In this procedure, one specifies the design lift coefficient, the cavitation number and the upper cavity thickness at two points along the profile chord. A prescribed pressure distribution shape is also selected. These quantities determine the profile design, which consists of the upper cavity and wetted surface contours, the design angle of attack, the cavity length, the drag coefficient, the moment coefficient and the lift-to-drag ratio. The method also includes off-design calculations in accordance with the direct theory of cavity flows, which determines the flow states for which interference can occur between the upper surface of the cavity and the upper nonwetted surface of the profile. The hydrodynamic performance of specific "point designs" is also given by these direct calculations. The chief new feature of the generalized design procedure is that it gives a designer the ability to prescribe two points on the cavity surface instead of one as heretofore. Although certain constraints must be observed by the designer when specifying these two values of cavity thickness, the third procedure is found to be more general and more flexible than design procedures studied previously. The necessary constraints are incorporated in the computer logic for the method. The fact that linearized theory is used tends to limit the applicability of the method to conceptual design and feasibility studies. The computer program for the procedure has been found to be economical and well suited for its intended purpose.

scholarly journals Comparison of Linear Vortex Panel Method and Finite Volume Method for Calculation of Generated Lift in Potential Flow Over Two-Dimensional Car Bodies

2020 ◽  
Author(s):  
Saeid Moammaei ◽  
Mehran Khaki Jamei ◽  
Morteza Abbasi
Keyword(s):  
Pressure Distribution ◽  
Lift Coefficient ◽  
Control Point ◽  
Panel Method ◽  
The Body ◽  
Aerodynamic Load ◽  
Two Dimensional ◽  
Algebraic Equations ◽  
Linear Algebraic Equations ◽  
The Impact

Abstract This paper describes one of the aspects of the panel method to analyze the aerodynamic characteristics of a sedan. The linear vortex panel method has been developed to simulate the ideal flow over a two-dimensional arbitrary car and, it also calculates the aerodynamic load on the body. By satisfying the boundary conditions on each control point, our linear algebraic equations are obtained. The results are sensitive to the distribution of the panels over the body thus the body is broken up equally into very small panels. After solving the set of equations, the vortices strength is obtained and the pressure distribution for the upper and the lower surface of the body is calculated. The impact of the angle of attack on the aerodynamic behavior of the intended car is investigated and it is found that the lift coefficient increases with the free stream angle from -4 to 4. The accuracy of the results has been determined by checking them against the standard CFD data. The pressure distribution trend is found very much in confirmation with the CFD results, however, a discrepancy at the rear end is observed. Therefore, it can be concluded that this method does not seem practical for geometries with steep slopes in the rear part of the car. Finally, both methods are applied to the other modified geometries with lower slopes at the rear section and the results compare well with the fluent.

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.

Wakes of Developed Cavities

1977 ◽  
Vol 21 (04) ◽  
pp. 225-238
Author(s):  
Jean-Marie Michel
Keyword(s):  
Free Surface ◽  
Boundary Conditions ◽  
Drag Coefficient ◽  
Cavity Length ◽  
Lift Coefficient ◽  
Cavity Flow ◽  
Numerical Results ◽  
Two Dimensional ◽  
Flow Configuration ◽  
Wake Model

A linearized wake model with a momentum defect is presented for the two-dimensional cavity flow around a base-vented foil which is placed in a free-surface channel. The numerical results show that, for a given cavity underpressureσ, the boundary conditions on the wake of the cavity have repercussions on the cavity length and the lift coefficient, whereas the drag coefficient is not modified. Similar features can be expected whenever the flow configuration is made strongly asymmetric by the external boundaries, especially by a free surface.

A Potential-Based Panel Method for the Analysis of a Two-Dimensional Super-or Partially-Cavitating Hydrofoil

1992 ◽  
Vol 36 (02) ◽  
pp. 168-181 ◽  
Author(s):  
C.-S. Lee ◽  
Y.-G. Kim ◽  
J.-T. Lee
Keyword(s):  
Cavity Length ◽  
Cavitation Number ◽  
Panel Method ◽  
Cavity Surface ◽  
Two Dimensional ◽  
Closure Condition ◽  
Surface Pressure Distribution ◽  
Cavity Closure ◽  
Cavitating Hydrofoil ◽  
Method Show

A potential-based panel method is presented for the analysis of a super-or partially-cavitating two-dimensional hydrofoil. The method employs normal dipoles and sources distributed on the foil and cavity surfaces. It is shown that the source plays an important role in positioning the cavity surface through an iterative process. The cavity closure condition is found very effective in generating the cavity shape. Upon convergence, the method predicts the cavitation number together with the lift, drag, and surface pressure distribution for a given cavity length. Systematic convergence tests of the present numerical method show fast and stable characteristics. Good correlations are obtained with existing theories and experimental results for both partially-and supercavitating flows.

Evaluation of Pressure Distribution on a Cavitating Hydrofoil With Flap

1967 ◽  
Vol 11 (02) ◽  
pp. 93-108
Author(s):  
Z. L. Harrison ◽  
Duen-pao Wang
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Pressure Distribution ◽  
Flat Plate ◽  
Flow Model ◽  
Wake Flow ◽  
Two Dimensional ◽  
The Moment ◽  
Cavitating Hydrofoil ◽  
General Method

A general method is established to calculate the pressure distribution and the moment of force for a two-dimensional, supercavitating hydrofoil with a flap. The wake flow model is adopted to describe the configuration of the flow field. Some numerical results for a supercavitating flat plate with a flap are compared with the corresponding experimental data.

Some Characteristics of Cavity Flow Past Cylindrical Inducers in a Venturi

1976 ◽  
Vol 98 (3) ◽  
pp. 461-466 ◽  
Author(s):  
B. C. Syamala Rao ◽  
D. V. Chandrasekhara
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Cavity Flow ◽  
Cavitation Number ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Wall Effects ◽  
Maximum Width ◽  
Shedding Frequency

The characteristic dimensions of the steady cavity and the shedding frequency of vortices behind six circular cylinders in a two-dimensional venturi have been studied. The normalized length and maximum width of cavity for cavitation sources of different sizes indicated unified trends with a modified cavitation number km. The angles of detachment θ increased with cavitation number k and decreased with increasing Reynolds number R. The Strouhal number Sd reached minimum values for all cavitation sources at small values of k. The possible role of wall effects on the investigations are discussed.

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.

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