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Abstract-A cable dynamics module was developed and implemented in the Reynolds Averaged Navier-Stokes Equations (RANS) solver CFDShip-Iowa to model the dynamics of towed cable systems in high sea states and during the launch and recovery of tethered underwater vehicles from behind a ship. In previous cable dynamics simulations, the vehicle forces are computed using hydrodynamic coefficients which are only accurate for steady, uniform flows. For unsteady, energetic flows in sea states and/or in the ship turbulent wakes, this coefficientbased approach is inadequate, and high-fidelity RANS solution is needed to predict the unsteady fluid forces acting on the vehicles. The cable module is based on an existing cable program with modifications for integration in CFDShip-Iowa and additional capabilities including dynamics modeling of the towing vehicle. The cable itself is represented by a series of rigid cylinders or links connected end-to-end by spherical joints. Cable physical parameters and external forces are lumped at these joints, and all vehicles are treated as rigid bodies. This paper focuses on the theoretical development of the cable module and presents sample simulations of an underwater vehicle towing another vehicle in both calm water and in Sea State 3. More extensive simulations and validations will be included in a future paper.

A microPCM fluid is a suspension of particles of microencapsulated phase-change-material (PCM) in a carrier heat transfer fluid. Such fluids have potential as pumped loop cooling media for applications in aerospace electronics cooling, terrestrial energy systems, and recently in electric vehicle cooling. The melting process of the phase change material does not occur at a single temperature but rather occurs over a temperature range. In the past, numerical solutions to microPCM fluids have assumed a linear release of latent heat over the phase change region. In this paper four analytic curve fits to differential scanning calorimeter measurements are made to better model the actual melting/solidification behavior. The numerical scheme models hydrodynamically fully developed laminar flow in a circular tube using the enthalpy method. The microPCM fluid contains 23% by weight microencapsulated octacosane particles in a 50/50% by volume ethylene glycol/water carrier fluid. A prescribed uniform heat flux at the tube wall is used. The solutions for these four cases include mixed mean exit temperature, axial tube wall temperature and local heat transfer coefficient.

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