scholarly journals Numerical study of helicopter blade–vortex mechanism of interaction using the potential flow theory

2012 ◽  
Vol 36 (7) ◽  
pp. 2841-2857 ◽  
Author(s):  
Patricia X. Coronado Domenge ◽  
Marcel Ilie
Keyword(s):  
Potential Flow ◽  
Numerical Study ◽  
Flow Theory ◽  
Helicopter Blade ◽  
Potential Flow Theory ◽  
Mechanism Of Interaction

A Two-Dimensional Experimental and Numerical Study of Moonpools With Recess

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Senthuran Ravinthrakumar ◽  
Trygve Kristiansen ◽  
Babak Ommani
Keyword(s):  
Potential Flow ◽  
Numerical Study ◽  
Domain Boundary ◽  
Flow Theory ◽  
Mode Shapes ◽  
Linear Potential ◽  
Two Dimensional ◽  
Potential Flow Theory ◽  
Mode Behavior ◽  
Piston Mode

Abstract Moonpool resonance is investigated in a two-dimensional setting in terms of regular, forced heave motions of a model with moonpool with different rectangular-shaped recess configurations. A recess is a reduced draft zone in the moonpool. Dedicated experiments were carried out. The model consisted of two boxes of 40 cm width each, with a distance of 20 cm between them. Recess configurations varying between 5 cm and 10 cm in length and 5 cm in height were tested. Different drafts were also tested. A large number of forcing periods and five forcing amplitudes were tested. A time-domain boundary element method (BEM) code based on the linear potential flow theory was implemented to investigate the resonance periods, mode shapes, as well as the moonpool response as predicted by the (linear) potential flow theory. Dominant physical effects were discussed, in particular damping due to flow separation from the sharp corners of the moonpool inlet and recess. The effect of the recess on the piston-mode behavior is discussed. The nondimensional moonpool response suggests strong viscous damping at the piston-mode resonance. The viscous BEM (VBEM) simulations demonstrate improvement over inviscid BEM, although further improvement of the method is needed. The VBEM simulations are, in general, in good agreement with the experiments. For the largest recess case, some discrepancies are observed in the amplitude-dependent response amplitude operators (RAOs). The piston-mode shapes are clearly different from the near flat free-surface elevation for a moonpool without recess, consistent with the recently published theory.

Application of Potential Flow Theory to Plane-Strain Extrusion

1967 ◽  
Vol 89 (3) ◽  
pp. 503-511 ◽  
Author(s):  
A. Shabaik ◽  
S. Kobayashi ◽  
E. G. Thomsen
Keyword(s):  
Plane Strain ◽  
Potential Flow ◽  
Flow Line ◽  
Flow Theory ◽  
Flow Fields ◽  
Potential Flow Theory ◽  
Good Agreement

Theoretical and experimental flow fields of several extrusion ratios of lead in plane strain were compared. It was found that, for extrusion ratios where dead metal exists, the agreement between the potential and experimental flow nets was better for small reductions when a modified boundary approaching a flow line was used. It was also found that when the flow changed direction gradually, the potential flow net was in good agreement with the experimental one. The solution obtained is unique and complete.

Passing Ship Effects in Non-Uniform Water Depth

2016 ◽  
Author(s):  
Lilan Zhou ◽  
Ji Yang ◽  
Qian Wang ◽  
Jiangtao Qin
Keyword(s):  
Time Domain ◽  
Potential Flow ◽  
Flow Model ◽  
Flow Theory ◽  
Propagation Model ◽  
Beach Erosion ◽  
Wave Flow ◽  
Generation Model ◽  
Theory Method ◽  
Potential Flow Theory

Waves generated by passing ships have potential adverse impacts on the environment (beach erosion, ecological disturbance, structures damage) and other waterway users (navigations, moored ships) in the coastal and sheltered areas. But issues related to waves of ships were addressed rarely in China until now. Accurate prediction of wash waves is the first step to control the washes from passing ships and it’s significant to reduce the effects of washes. A coupled method is used in this paper to simulate the washes and its effects caused by the passing ship. A potential flow theory method is adopted as the stationary wave generation model; a non-hydrostatic wave flow model is used as the wave propagation model; a time domain method is chosen as the model for simulating the forces and moments of mooring ship. The waves calculated by a potential flow theory method in the near field are used as the input for the non-hydrostatic wave-flow model to obtain the far field waves. A time-domain representation of the wave-cut at the location of the passing vessel is transformed to the frequency-domain and is used as the input for the diffraction computations. Parts of the calculated results are validated experimentally, satisfactory agreement is demonstrated.

scholarly journals EVALUATION OF THE ADDED RESISTANCE AND SHIP MOTIONS COUPLED WITH SLOSHING USING POTENTIAL FLOW THEORY

Brodogradnja ◽  
2016 ◽  
Vol 67 (4) ◽  
pp. 109-122
Author(s):  
Ivana Martić ◽  
◽  
Nastia Degiuli ◽  
Ivan Ćatipović
Keyword(s):  
Potential Flow ◽  
Flow Theory ◽  
Ship Motions ◽  
Added Resistance ◽  
Potential Flow Theory

Study on the Dynamics of the Bubble under the Combined Action of the Bjerknes Effect of the Free Surface and the Buoyancy

2014 ◽  
Vol 644-650 ◽  
pp. 628-631
Author(s):  
Ke Yi Li ◽  
Zhong Cai Pei
Keyword(s):  
Free Surface ◽  
Boundary Element Method ◽  
Boundary Element ◽  
Potential Flow ◽  
Flow Theory ◽  
Motion Direction ◽  
Potential Flow Theory ◽  
Combined Action ◽  
Element Method

When the bubble moves in the vicinity of a free surface, the movement will be affected by the buoyancy and the Bjerknes effect. Blake and Gibson proposed the criterion which determined the motion direction of the jet and the dynamics of bubble. They proposed the jet wouldn’t be formed in the condition that . Based on the potential flow theory, boundary element method (BEM) is used to calculate three typical examples in this paper in order to study the dynamics of the bubble under the combined action of the Bjerknes effect of the free surface and the buoyancy. It is found out during the analysis that the Blake criterion is applicable to predict the conditions that and .

Study on the Aerodynamics Mechanism of Passenger Car under Unsteady Crosswind

2013 ◽  
Vol 631-632 ◽  
pp. 809-816
Author(s):  
Chen Shen ◽  
Hui Zhu ◽  
Zhi Gang Yang
Keyword(s):  
Empirical Formula ◽  
Potential Flow ◽  
Aerodynamic Force ◽  
Vortex Motion ◽  
Flow Theory ◽  
Potential Flow Theory ◽  
Practical Engineering ◽  
Precise Prediction ◽  
Engineering Significance ◽  
Semi Empirical

Regular formulae for lateral aerodynamic force cannot give precise prediction under unsteady crosswind. By generalizing potential flow theory and taking the aerodynamic derivative into consideration, the semi-empirical expression for lateral aerodynamic force is derived. In order to determine the coefficients in the semi-empirical formula, the model of a typical double-deck coach is investigated in a sequence of numerical simulations under pure crosswind condition (i.e. linear crosswind, pseudo-step crosswind, sinusoidal crosswind). Moreover, advantages of the semi-empirical formula over the regular one are revealed. Further inspections into the flow field derived from the theory of vortex motion indicate that the deviation between the prediction given by semi-empirical formulae and that by numerical simulation is caused by the non-viscous assumption in potential flow theory. The lateral aerodynamic force depends linearly on the crosswind aerodynamic derivative. Situations in which the coach is moving in the direction perpendicular to the wind velocity are also studied to find the cause of the error in semi-empirical formula. Furthermore, the semi-empirical formula is revised by introducing the “damping model method”. A relatively complete system of prediction for lateral aerodynamic force on a coach, which is of practical engineering significance, has been constructed.

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