This paper numerically investigates the ditching characteristics of the NACA TN 2929 model. In the simulation method, the Reynolds-averaged Navier-Stokes equation and realizable k-ε turbulence model are solved by the finite volume method; the volume-of-fluid method is used to capture the water-air interface; the six-degree-of-freedom model and the global-moving-mesh method are used to deal with the relative motion between the water and the object. Global moving mesh is a new dynamic-mesh method, which is proposed to simulate water-entry problems. In global moving mesh, the whole computational domain and boundaries move together with the object to avoid the high computational expense and low-quality mesh in the traditional mesh-deformation method. This numerical method is applied to simulate the water impact of a two-dimensional cylinder in free fall, and the results show a good agreement with the experimental data. The effect of each aerodynamic part of the NACA TN 2929 model on the ditching behavior is studied in detail, and the results show that aerodynamic loads cannot be ignored when analyzing the ditching motion of the aircraft. Nomenclature a = volume fraction in a cell C p = pressure coefficient f = force K = inertial tensor L = overall length of the fuselage M = moment vector m = mass of an object _ m = mass transfer between different fluids N = number of phases in a multiphase flow p = pressure S = source term V 0 = impact velocity v = velocity vector z = vertical distance of the center of gravity above calm water level θ = radial angle of a cylinder ρ = density ω = angular-velocity vector Subscripts b, g = value in body or inertial coordinate systems k, q = kth fluid and qth fluid ref = reference value w = water
This paper numerically investigates the ditching characteristics of the NACA TN 2929 model. In the simulation method, the RANS equation and realizable k-ε turbulence model are solved by the finite volume method; the volume-of-fluid method is used to capture the water-air interface; the six degree of freedom model and the global moving mesh (GMM) method are used to deal with the relative motion between the water and the object. GMM is a new dynamic mesh method which is proposed to simulate water entry problems. In GMM, the whole computational domain and boundaries move together with the object to avoid the high computational expense and low quality mesh in the traditional mesh deformation method. This numerical method is applied to simulate the water impact of a 2D cylinder in free fall, and the results show a good agreement with the experimental data. The effect of each aerodynamic part of the NACA TN 2929 model on the ditching behavior is studied in detail, and the results show that aerodynamic loads cannot be ignored when analyzing the ditching motion of the aircraft. Nomenclature a = volume fraction in a cell p C = pressure coefficient f = force K = inertial tensor L = over-all length of the fuselage m = mass of object m = mass transfer between different fluids M = moment vector N = number of the phases in a multiphase flow p = pressure S = source term v = velocity vector 0 V = impact velocity z = vertical distance of the center of gravity above calm water level ρ = density
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