1. In the particular arrangement shown in Fig. 2, the output beams, which have already passed through the measurement volume, are reflected by the dichroic mirror DM1toward the lens L3(identical in focal length to L1), which then refocuses them. The beams reflected by the mirror DM2are directed toward the retro-reflector Mrfor IRS use. A third dichroic mirror DM3, centered at532 nmwith maximum reflectivityat 45deg, furtherreduces the beam's energy. Angular tuning of this mirror around the maximum reflectivity position allows adjusting the transmitted energy toward the focal plane camera (FPC). Depending on the beam energy, neutral density filters (not shown) can be introduced in the optical path to reduce the beams' intensity before reaching the camera. A microscope objective lens L4(48 mm, chosen for the desired magnification), is placed near the focal region of lens L3to form a magnified image of the crossing beams region on the FPC. The iris, IR, is used to remove stray light and secondary images of the beams that are formed by the dichroic mirrors. Different planes near the crossing point of thebeams canbeobserved as thelensL4andthecameraaresimultaneouslytranslatedparalleltotheopticalaxis. D. Interferogram Processing
2. Anumerical simulation of the jet flow without co-flow was performed using the VULCAN CFD code.13This code is able to simulate finite-rate chemically reacting flow-fields using a finite-volume discretization of the Favreaveraged Navier-Stokes equations. The inviscid fluxes were computed using Edward's low dissipation flux split scheme in conjunction with a3rdorderMUSCLstencilandalimiterbyvanLeer.Turbulencewasmodeledusingthe Wilcox k-omega model. In order to include the effects of turbulence generated in the facility combustor, the flow in the combustor was solved in addition to the external flow. The combustor grid had 30,720 points and the external grid had 473,088 points. A slight pressure gradient was applied across the external domain to mimic the flow through the test cell and to aid convergence by convecting starting vortices downstream and out of the solution domain. To reduce the computational time, the chemical composition of the combustor flow corresponds to a postcombustion composition. The chemical composition was assumed to be N2(0.611781/mol), O2(0.19601/mol), H2O (0.17857/mol), and Ar (0.00761/mol). The total temperature and pressure in the combustor were 1468.7 K and 4.217 atm. Wall functions were used to reduce grid spacing requirements near walls. An isothermal boundary condition with a wall temperature of 330 K was used for all surfaces. The solutions were computed solving the combustor flow-field first followed by the external flow-field. The combustor grid was converged 5.5 orders of magnitude and the externalgridwas converged6.4ordersof magnitude.
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