Application of the Unsteady-Lifting-Surface Theory to the Study of Propeller-Rudder Interaction

1970 ◽  
Vol 14 (03) ◽  
pp. 181-194
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs ◽  
M. R. Ali
Keyword(s):  
Numerical Procedure ◽  
Ideal Incompressible Fluid ◽  
Operator Technique ◽  
Surface Integral ◽  
New Approach ◽  
Surface Theory ◽  
Lifting Surface ◽  
Harmonic Components ◽  
Lifting Surfaces ◽  
Interaction Problem

The propeller-rudder interaction problem is studied by means of the unsteady-lifting- surface theory. Both surfaces of arbitrary geometry are immersed in a non-uniform flow- field (i.e., hull wake) of an ideal incompressible fluid. The boundary-value problem yields a pair of surface integral equations, the inversion of which is achieved by the so- called "generalized lift operator" technique, a new approach developed by the authors, in conjunction with the presently used "mode-collocation" method. The analysis demonstrates the mechanism of the interaction phenomenon by exhibiting the filtering effects of the propeller on the harmonic constituents of the wake which allow the rudder to be exposed only to the blade harmonic and multiples thereof. A numerical procedure adaptable to the CDC 6600 computer has been developed which furnishes information about (i) the steady and time-dependent pressure distribution on both lifting surfaces, and (ii) the resultant hydrodynamic forces and moments. A limited number of calculations exhibit the importance of some parameters such as axial clearance, number of blades, and harmonic components of the hull wake.

Application of Lifting-Surface Theory to the Prediction of Hydroelastic Response of Hydrofoil Boats

1968 ◽  
Vol 12 (04) ◽  
pp. 286-301
Author(s):  
C. J. Henry
Keyword(s):  
Equations Of Motion ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Mode Shapes ◽  
Operator Technique ◽  
Elastic Mode ◽  
Surface Theory ◽  
Lifting Surface ◽  
Modes Of Vibration ◽  
Elastic Modes

In this report a theoretical procedure is developed for the prediction of the dynamic response elastic or rigid body, of a hydrofoil-supported vehicle in the flying condition— to any prescribed transient or periodic disturbance. The procedure also yields the stability indices of the response, so that dynamic instabilities such as flutter can also be predicted. The unsteady hydrodynamic forces are introduced in the equations of motion for the elastic vehicle in terms of the indicia I pressure-response functions, which are de rived herein from lifting-surface theory. Thus, the predicted vehicle-response includes the effects of three-dimensional unsteady flow conditions at specified forward speed. The natural frequencies and elastic modes of vibration of the vehicle and foil system in the absence of hydrodynamic effects are presumed known. A numerical procedure is presented for the solution of the downwash integral equations relating the unknown indicial pressure distributions to the specified elastic-mode shapes. The procedure is based on use of the generalized-lift-operator technique together with the collocation method.

Propeller Loading Distributions

1969 ◽  
Vol 13 (04) ◽  
pp. 237-257
Author(s):  
S. Tsakonas
Keyword(s):  
Numerical Procedure ◽  
New Approach ◽  
Surface Theory ◽  
Linearly Independent ◽  
Lifting Surface ◽  
Numerical Program ◽  
Theoretical Results ◽  
Made In

The present study reports the improvements made in the numerical procedure for evaluating propeller loading distributions which had been developed at Davidson Laboratory by adaptation of the unsteady-lifting-surface theory. A new approach, based on the fact that the assumed Birnbaum chordwise modes are not linearly independent, has achieved stability for the chordwise distribution, which had otherwise shown no sign of convergence with increasing number of modes. Other refinements of the numerical program, including provision for arbitrary blade camber variation and overlapping of blade wakes, have improved the accuracy of both chordwise and spanwise loading distributions and brought the theoretical results closer to experiment.

Propeller Loading-Induced Velocity Field by Means of Unsteady Lifting Surface Theory

1973 ◽  
Vol 17 (03) ◽  
pp. 129-139
Author(s):  
W. R. Jacobs ◽  
S. Tsakonas
Keyword(s):  
Velocity Field ◽  
High Speed ◽  
Pressure Field ◽  
Numerical Procedure ◽  
Nonuniform Flow ◽  
Surface Theory ◽  
Loading Function ◽  
Lifting Surface ◽  
Space Function ◽  
Induced Velocity

An analysis based on the lifting surface theory has been developed for evaluation of the vibratory velocity field induced by the loading of an operating propeller in both uniform and nonuniform inflow fields. The analysis demonstrates that in the case of nonuniform flow the velocity at any field point is made up of a large number of combinations of the frequency constituents of the loading function with those of the space function (propagation or influence function). A numerical procedure has been developed adaptable to a high-speed digital computer (CDC 6600), and the existing program, which evaluates the steady and unsteady propeller loadings, the resulting hydrodynamic forces and moments, and the pressure field, has been extended to include evaluation of the velocity field as well. This program should thus become a highly versatile and useful tool for the ship researcher or designer.

Propeller-Rudder Interaction Due to Loading and Thickness Effects

1975 ◽  
Vol 19 (02) ◽  
pp. 99-117
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs ◽  
M. R. All
Keyword(s):  
Numerical Procedure ◽  
Thickness Effect ◽  
Thin Body ◽  
Propeller Blade ◽  
Blade Thickness ◽  
The Mean ◽  
Axial Clearance ◽  
Lifting Surfaces ◽  
Thrust And Torque ◽  
Interaction Problem

The previous analysis of the propeller-rudder interaction problem by means of the lifting-surface theory has been modified to include the effects of thickness of both surfaces. The effect of propeller blade thickness and rudder thickness on the "flow displacement" in the field is taken into account by the "thin body" approach. The blade thickness effect on the loading of the propeller blade due to its nonplanar form, being small, is neglected. The resulting onset velocities on both lifting surfaces due to the thickness effects on the flow field are incorporated, together with the onset velocities due to hull wake and camber and incident angle of the surfaces, into the existing iterative procedure. The numerical procedure, which has been adapted to the CDC 6600 high speed digital computer, furnishes the steady and time-dependent pressure distributions on both lifting surfaces and the resulting hydrodynamic forces and moments. From the limited number of calculations, it is seen that the thickness effect does not change the general conclusions reached in the previous study of the interaction problem. The interaction apparently is governed principally by the loading effects. The mean and blade-frequency thrust and torque and the mean rudder force and moment are very little affected by the inclusion of thickness even at the smallest possible axial clearance between propeller and rudder. The influence of thickness is greater on the propeller bearing forces and bending moments, on the steady-state values more than on the unsteady, and decreases with increase in axial clearance. The thickness effect is most pronounced in the case of unsteady rudder forces and moments at certain axial clearances, varying cyclically with clearance.

Unsteady Lifting Surface Theory for a Marine Propeller of Low Pitch Angle With Chordwise Loading Distribution

1965 ◽  
Vol 9 (03) ◽  
pp. 79-101 ◽  
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Weighted Average ◽  
Marine Propeller ◽  
Surface Integral ◽  
Dimensional Solution ◽  
Surface Theory ◽  
Lifting Surface ◽  
Blade Area ◽  
Thrust And Torque

This study is third in a series of investigations applying the unsteady lifting-surface theory to the marine propeller case. In the present investigation, the surface integral equation is solved for a mathematical model where the chordwise loading is taken as the first term of Birnbaum's lift distribution (flat-plate chordwise distribution), in conjunction with Glauert's lift operator, which, in essence, satisfies the chordwise boundary conditions by a weighted average. It is shown that this model is an improvement over the modified Weissinger model used previously in this series, because it contains as a nucleus the exact two-dimensional solution, and thus it provides a sounder basis for determining the three-dimensional effects. The blade-loading is determined for a propeller operating in flow disturbances induced by the presence of a hull and by the blade-camber and incidence-angle effects. The stationary loading obtained by the present model is less than that obtained by the modified Weissinger model, whereas the nonstationary loading is slightly larger. The results of numerical calculations are applied to the problem of propeller vibratory thrust and torque, and comparison is made with previous theoretical and experimental values. Conclusions of the earlier studies as to the dependence of loading on the important parameters—blade-area ratio, aspect ratio and pitch—are confirmed by the present results.

An “Exact” Linear Lifting-Surface Theory for a Marine Propeller in a Nonuniform Flow Field

1973 ◽  
Vol 17 (04) ◽  
pp. 196-207 ◽  
Author(s):  
S. Tsakonas ◽  
W. R. Jacobs ◽  
M. R. Ali
Keyword(s):  
Considerable Increase ◽  
Present Model ◽  
Numerical Procedure ◽  
Computer Time ◽  
Nonuniform Flow ◽  
Blade Loading ◽  
Surface Theory ◽  
Marine Propellers ◽  
Lifting Surface ◽  
The Mathematical Model

The mathematical model used in previous Davidson Laboratory adaptations of linearized unsteady lifting surface theory to marine propellers has been revised by removing the so-called "staircase" approximation of the blade wake and replacing it by an "exact" helicoidal blade wake. A new numerical procedure and program based on the present model have been developed to evaluate the steady and unsteady blade loading distributions, which are used to determine the bearing forces and moments. Systematic calculations of these forces and moments for a series of propellers show better agreement on the whole with experimental measurements than did the earlier calculations for the same series. In addition, the chordwise loading distributions are much smoother than obtained previously. However, the quantitative improvement must be weighed against the considerable increase in computer time over the old method.

Continuity of lifting surface theory in subsonic and supersonic flow

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 1788-1791
Author(s):  
Tetsuhiko Ueda
Keyword(s):  
Supersonic Flow ◽  
Surface Theory ◽  
Lifting Surface
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