Computation of Compressible Flows Through a Chemical Laser Device with Crossflow Injection

Abstract

The Air Force Research Laboratory has an ongoing effort to develop an accurate and ef cient computational tool to support the development of advanced chemical oxygen/iodine laser (COIL) devices. In this study, a series of computational simulations have been performed to provide a better understanding of uid dynamic phenomena within geometries associated with COIL ow elds. The parallel, implicit unstructured Navier-Stokes code Cobalt 60 was used to compute laminar, turbulent, and unsteady ows of helium within the research assessment and device improvement chemical laser (RADICL) nozzle. Computational results showing details of the jet mixing interaction and topological structure are presented. The laminar and turbulent results obtained with Cobalt 60 are in excellent agreement with measured mass ow rates and surface pressure data obtained from recent cold-ow tests performed with the RADICL device. Insuf cient experimental measurement prevents the determination of whether or not transition occurs within the injector region. The laminar time-accurate results indicate small-scale unsteadiness in the frequency range of 200 kHz downstream of the nozzle throat. Nomenclature A = cross-sectional area A, B, C, D = grid labels (D is nest grid) a = speed of sound a, b, c = viscous terms in energy equation [see Eq.(2)] c t1x , c t2x = x-direction convection terms for turbulence c t1 y , c t2 y = y-direction convection terms for turbulence c t1 z , c t2 z = z-direction convection terms for turbulence D = diameter of injector D = volumetric source term vector D t1 , D t 2 = source terms for turbulence closure equations dS = differential surface dV = differential volume E t = total energy, ½[e 1 2 .u 2 v 2 w 2 /] f , g, h = x, y, and z components of inviscid uxes i , j , k = Cartesian unit vectors k = thermal conductivity, turbulence kinetic energy M = Mach number M = molecular weight n = normal distance from wall n = molar ow rate n = unit normal vector p = pressure Q = vector of conserved variables Re = Reynolds number r; s; t = x, y, and z components of viscous uxes S = surface of control volume T = temperature t = time u, v, w = Cartesian components of velocity

Quantitative Mixing Measurements of a Supersonic Injection COIL Nozzle with Trip Jets

“…Injecting the iodine in the subsonic region promotes mixing between the injected iodine and the primary oxygen flows, whereas diffusive mixing is difficult in the supersonic region because of compressibility effects. A well-mixed medium increases the interaction between O 2 ( 1 Δ) and iodine, to produce more I * ( 2 P and Masuda et al [5][6][7][8][9] These simulations were performed to investigate the spatial and temporal gradients in the flowfield, which impact the laser beam quality.…”