Accession Number : ADA187710

Title :   Numerical Simulations of the Wake Downstream of a Twin-Screw Destroyer Model.

Descriptive Note : Memorandum rept.,

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : Swean, T F , Jr

PDF Url : ADA187710

Report Date : 11 Dec 1987

Pagination or Media Count : 37

Abstract : The parabolic, incompressible, time-averaged Navier-Stokes equations together with a two-equation (K,epsilon), model of turbulence are used to numerically simulate the turbulent wake behind a self-propelled model of a twin-screw destroyer. Experimental data are employed to initialize the fluid state in a transverse plane 10.0 ft downstream of the stern from which point the wake evolution is computed to a plane 30.0 ft downstream. Two propeller operating conditions are considered, outboard propeller rotation and inboard propeller rotation. In the outboard simulation, the propeller thrust is bifurcated into upper and lower regions, the former of which eventually is convected to the free surface where the upwelling displaces the drag wake to outboard. This evolution combined with locally high levels of turbulence kinetic energy results in high transverse strain and transverse Reynolds stress in the surface region. In the inboard simulation the thrust wake remains unimodal and spatially stationary within the local transverse plane. Initial and small levels of velocity excess near the wake centerline quickly dissipate as the port and starboard drag wake merge into a single diffuse velocity deficit structure. This results in considerably smaller transverse strain than in the outboard rotation simulation. Keywords: Marine propellers; Turbulent ship wake; Self-propelled wake; Finite-element calculations.

Descriptors :   *DRAG, *MARINE PROPELLERS, *TURBULENCE, *WAKE, EVOLUTION(GENERAL), EXPERIMENTAL DATA, FINITE ELEMENT ANALYSIS, INBOARD, KINETIC ENERGY, MEAN, MATHEMATICAL MODELS, MOMENTUM TRANSFER, NAVIER STOKES EQUATIONS, NUMERICAL ANALYSIS, OUTBOARD, ROTATION, SELF PROPELLED, SHIPS, COMPUTERIZED SIMULATION, STRESSES, SURFACES, THRUST, TIME, TRANSVERSE, UPWELLING, VELOCITY, DESTROYERS, MODEL TESTS, BIFURCATION(MATHEMATICS)

Subject Categories : Fluid Mechanics
      Marine Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE