The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform

Narayanan Komerath - One of the best experts on this subject based on the ideXlab platform.

  • Correlation of Unsteady Pressure and Inflow Velocity Fields of a Pitching Rotor Blade
    Journal of Aircraft, 1995
    Co-Authors: Mihir Lal, S. G. Liou, G. A. Pierce, Narayanan Komerath
    Abstract:

    Predictions from four different analytical methods are compared with measurements of unsteady inflow velocity and surface pressure Distributions on a pitching rotor blade in hover. The test case is a stiff two-bladed teetering rotor constructed from full-scale tail rotor blades, subjected to w/rev simple harmonic pitch oscillations under incompressible flow conditions. The chordwise Distributions of unsteady pressure at three radial locations on the blade are compared with Theodorsen's and Loewy's two-dimensional incompressible unsteady aerodynamic theories and with Kaladi's pulsating Doublet Distribution method. Inflow velocity is predicted successfully using Peters' modal theory for steady as well as dynamic pitch conditions. The effect of dynamic inflow on rotor unsteady surface pressure is studied. At inboard radial locations, Loewy's two-dimensional theory for even harmonics of forcing frequency and Theodorsen's two-dimensional theory for odd harmonics provide efficient and reliable predictions of unsteady blade surface pressure. At outboard radial locations, panel or modal methods have to be used to predict amplitude and phase of unsteady pressure. Tip effects, mean pitch angle effects, and effects of rotation have been demonstrated. Nomenclature b = number of blades C(k) — Theodorsen's lift deficiency function, F + IG C'(k) = modified lift deficiency function for the rotor, F' + iG' Cp = pressure coefficient, 2(p - p y)/pfl2r2

S B Suh - One of the best experts on this subject based on the ideXlab platform.

  • A BILINEAR SOURCE AND Doublet Distribution OVER A PLANAR PANEL AND ITS APPLICATIONS TO SURFACE PANEL METHODS
    1994
    Co-Authors: J C Suh, J T Leet, S B Suh
    Abstract:

    This paper presents closed-forms for computing the induced potentials and velocities due to a bilinear density Distribution of surface and/or Doublet singularities over a planar panel. The surface integrals associated with Green's scalar identity can be transformed into contour integrals using Stokes' formulas. The analysis includes the cases of constant or linear Distributions. The closed-forms are more computer-oriented and explicit than those derived previously so that the matrix elements of the linear system of algebraic equations in application of surface panel methods can be obtained with much easier implementation.

S. Morioka - One of the best experts on this subject based on the ideXlab platform.

  • Phenomenological viscous factor in the nonequilibrium Distribution function for liquids
    Physical Review E, 2005
    Co-Authors: S. Morioka
    Abstract:

    An improved formula of shear viscosity for liquids is presented by introducing a phenomenological viscous factor in the nonequilibrium term in the Doublet Distribution function, which improves an incomplete formula of shear viscosity presented in an early work of Born and Green. The phenomenological viscous factor effectively counts some higher-order interactions, and is constrained so that, in the limit of hard-sphere liquids, the magnitude of the improved formula of shear viscosity reduces to that of Enskog for dense fluids. The improved formula does not require any adjustable parameters except for the pair potential to describe liquids. In order to verify the improved formula, a liquid of Ar near the triple point is studied in detail. In addition, liquids of Pb in wide ranges of temperature are examined to test the temperature dependence of the phenomenological viscous factor. Here an available integral equation is employed to calculate the radial Distribution function by prescribed pair potentials. One finds that the present formula is capable to describe the shear viscosity in accord with those of experimental data for both cases of Ar and Pb. The phenomenological viscous factor plays a crucial role in the evaluation of shear viscosity for liquids.

Baowei Song - One of the best experts on this subject based on the ideXlab platform.

  • Prediction of tip vortex cavitation inception with low-order panel method
    Ocean Engineering, 2016
    Co-Authors: Youjiang Wang, Moustafa Abdel-maksoud, Ke-qi Wang, Baowei Song
    Abstract:

    Abstract Tip vortex cavitation is the first type of cavitation to take place in most cases. Because it always produces radiated noise, avoiding or at least delaying tip vortex cavitation is crucial for achieving low radiated noise emissions. The present study aims to predict the tip vortex cavitation inception with the low-order panel method, which is widely used at the early propeller design stage. First, a velocity smoothing parameter varying with the age of vortex is adopted to align the wake. This leads to a wake shape that coincides very well with the wake pattern from a RANS solver. A consistent formula for evaluating the smoothing parameter for different cases is also achieved with the fitting method. Second, the tip vortex circulation is calculated based on the converged wake shape and Doublet Distribution. This procedure is found to be independent from the panel size. Finally, based on the minimum pressure Distribution along the tip vortex, cavitation inception numbers are obtained for the Potsdam Propeller Test Case (PPTC) and the propeller 4383 developed in NSRDC. The results show a good agreement with the experimental measurements.

Wang Guoqiang - One of the best experts on this subject based on the ideXlab platform.

  • Prediction of unsteady performance of propeller by potential based panel method
    Journal of Ship Mechanics, 2006
    Co-Authors: Wang Guoqiang
    Abstract:

    A numerical method to predict the unsteady performance of the propeller is presented by using potential based panel method,in which hyperboloidal quadrilateral panels with constant source and Doublet Distribution are employed and equal pressure Kutta condition at trailing edge is applied.A corresponding computer program is developed for this purpose.Two propellers,HSP and D4679,proposed by Propulsion Committee of 22nd ITTC and a propeller PF-W-B supplied by MARINTEK are taken as examples for validation.Comparison with experimental data and calculated results obtained by other researchers shows good agreement.