Numerical Simulation of Rolling Stability of Flight Vehicle

Large lift-to-drag ratio,high maneuverability,and good controllability are the basic performance for flight vehicles.Studying the rolling stability problems of a high lift-to-drag ratio aircraft is of great significance to the safety and control in maneuvering flight.The research on the static stability in the rolling direction of a HTV-2 like shape under a typical Mach number and attack angle was carried out.Similarly,by using Euler,laminar,turbulence and transition models,investigations of the dynamic stability in a single degree of freedom rolling motion of the same shape structure were executed.The numerical results show that the dynamic derivative of Euler is the largest,and the dynamic derivatives resulting from laminar,turbulence,and transition models are not much different.

Roll shifting strategy with varying stroke and step in hot strip mill

A new roll shifting strategy with varying stroke and varying step was investigated,Two characteristic parameters including cat ear height and gap contour smoothness were introduced to assess the effect of shifting strategy on roll wear,and the relation between characteristic parameters and shifting strategy was established.Both varying stroke and varying step can reduce cat ear height and gap contour smoothness,so the shifting strategy with varying stroke and varying step is better than the one with either varying stroke or varying step,Based on the effect of shifting control parameters on characteristic parameters of roll wear,the selection principle of these shifting control parameters was gained.A case study was conducted to validate the proposed roll shifting strategy,reducing uncontrollable quartic loading gap contour,improving strip profile and extending rolling length of a rolling campaign.

Computational Fluid Dynamics Uncertainty Analysis for Simulations of Roll Motions for a 3D Ship

The roll motions are influenced by significant viscous effects such as the flow separation.The 3D simulations of free decay roll motions for the ship model DTMB 5512 are carried out by Reynold averaged NavierStokes(RANS) method based on the dynamic mesh technique.A new moving mesh technique is adopted and discussed in details for the present simulations.The purpose of the research is to obtain accurate numerical prediction for roll motions with their respective numerical/modeling errors and uncertainties.Errors and uncertainties are estimated by performing the modern verification and validation(V&V) procedures.Simulation results for the free-floating surface combatant are used to calculate the linear,nonlinear damping coefficients and resonant frequencies including a wide range of forward speed.The present work can provide a useful reference to calculate roll damping by computational fluid dynamics(CFD) method and simulate a general ship motions in waves.