Numerical prediction of hydrodynamics characteristics of modern marine propulsive device in steady flow

Abstract

A potential based Surface Panel Method (SPM) is applied to the hydrodynamic analysis of modern marine propuslve device, i.e., podded propulsion system (PI'S) in steady flow. At first the surface of the body is approximated by a number of small hyperboloidal quadri lateral panel, with constant sources and doublet distributi(ms. The surface of the trailing vortex sheet is also represented by hyperboloidal quadrilateral panels with constant doublet distributions. The strengths of source <lnd doublet are determined by solving the boundary vallie problem at control point of each panel surface satislYing some boundaI)' cond itions. Effect of viscosity is incorporated to the potentia! solution using Prandtl-Schlieting formula. The method Is first applied to analyze pod, strut and propeller separately, then the combination of pod.strut geometry and finally the complete pod propllision system, PI'S (Propeller +Pod + Strut). Appling this method. the pressure distribution on the pod and strut lIsed in podded propeller system are determined and compared with published re~ults. The method is also u,ed to evaluate effects of h"b taper angle and pod-strut geometry on the open water ehara~teriBtics of a fixed pitch SCrew propeller "sed in podded propulsion system in pusher configuration. The method i~ validated by comparing the predicted reSlllts with experimental measurements. Effects of huh taper angle on hydrodynamic characteristics are studied numerically in terms of thrust coefficient, torque coefficient, and propulsive efficiency for a wide range of advance coefficient In case of hub taper angles of 0°, 5",10°,15°,20" and 25° in pusher configuration. The effect of pod-strut geometry on the hydrodynamic vi characteristics of tapered fi"ed pitch SCrewpropellers used in pusher podded propulsion system; has also been studicd nllmerically. Different pod-_,trut configllrations arc modeled for tapered hub propellers with hub taper angles 01'0°,5", lIJo, 15°, 20a and 25° respectively. 1n this case, only the characteristics of the propeller are predicted in pre,ence of pod"strut geometry (propeller with pod-strut). In other word, blockage effect due to the presence ofpod-,lrut body is taken into account ignoring the losses due to skin friction imposed by that body. Maior findings include well agreement of results predicted by the method with measurement, ,ignitieant effects of hub taper angle On hydrodynamic characteristics of propellers, c()llsiderable increase in hydmdynamic characteristics of propeller- when podstrut body is aUaehed forward to it in pusher configuration.