Modeling of near-continuum laminar boundary layer shocks using DSMC

The hypersonic flow of nitrogen gas over a double wedge was simulated by the DSMC method using two-dimensional and three-dimensional geometries. The numerical results were compared with experiments conducted in the HET facility for a high-enthalpy pure nitrogen flow corresponding to a free stream Mach number of approximately seven. Since the conditions for the double wedge case are near-continuum and surface heat flux and size of the separation are sensitive to DSMC numerical parameters, special attention was paid to the convergence of these parameters for both geometries. At the beginning of the simulation, the separation zone was predicted to be small and the heat flux values for the 2-D model were comparable to the experimental data. However, for increasing time, it was observed that the heat flux values and shock profile strongly deviated from the experiment. Investigation of a three-dimensional model showed that the flow is truly three-dimensional and the side edge pressure relief provides good agreement between simulations and the experiment

Factors influencing flow steadiness in laminar boundary layer shock interactions

The Direct Simulation Monte Carlo method has been used to model laminar shock wave boundary interactions of hypersonic flow over a 30/55-deg double-wedge and “tick-shaped” model configurations studied in the Hypervelocity Expansion Tube facility and T-ADFA free-piston shock tunnel, respectively. The impact of thermochemical effects on these interactions by changing the chemical composition from nitrogen to air as well as argon for a stagnation enthalpy of 8.0 MJ/kg flow are investigated using the 2-D wedge model. The simulations are found to reproduce many of the classic features related to Edney Type V strong shock interactions that include the attached, oblique shock formed over the first wedge, the detached bow shock from the second wedge, the separation zone, and the separation and reattachment shocks that cause complex features such as the triple point for both cases. However, results of a reacting air flow case indicate that the size of the separation length, and the movement of the triple point toward to the leading edge is much less than the nitrogen case

Linear Instability of Shock-Dominated Laminar Hypersonic Separated Flows

The self-excited spanwise homogeneous perturbations arising in shock-wave/boundary-layer interaction (SWBLI) system formed in a hypersonic flow of molecular nitrogen over a double wedge are investigated using the kinetic Direct Simulation Monte Carlo (DSMC) method. The flow has transitional Knudsen and unit Reynolds numbers of 3.4 x 10$^{-3}$ and 5.2 x 10$^4$ m$^{-1}$, respectively. Strong thermal nonequilibrium exists downstream of the Mach 7 detached (bow) shock generated due to the upper wedge surface. A linear instability mechanism is expected to make the pre-computed 2-D base flow potentially unstable under spanwise perturbations. The specific intent is to assess the growth rates of unstable modes, the wavelength, location, and origin of spanwise periodic flow structures, and the characteristic frequencies present in this interaction.Comment: 10 pages, 6 figures. To appear in the proceedings of the IUTAM Transition 201

Detection of heavy metal concentrations in soil caused by Nigde city garbage dump

WOS: 000248746200020The aim of this study was to detect heavy metal concentrations in the creek which passes through Nigde city garbage dump. In this respect, the soil samples collected in the study area by GPS were analyzed using X-Ray Fluorescence Spectrometer. Traces of heavy metals were observed by using statistical programs on analysis results. Geological observations were taken into consideration. According to the heavy metal concentrations in the Creek, the maximum values were as follows; (mg/ kg) Ti: 4960, V: 520, Cr: 120, Mn: 8 10, Ni: 460, Cu: 4 10, Zn: 100 and Pb: 480. The concentration levels of heavy metals in soil caused by garbage dump are listed in the following order; Pb > Cu > V > Ti > Cr > Ni > Zn. High positive correlation were observed between Ti-Mn, V-Ni and Cr-Ni. Medium positive correlations were observed between V-Cr, V-Cu and Ni-Zn. It has been found by chemical analysis data collected from stations established throughout the creek that there is an effect of morphological structure and no geological anomaly has been formed. According to chemical analysis results, statistical programs give important accuracy. Heavy metals, which give anomaly, differ throughout the creek. The source of these heavy metals was determined as Nigde city garbage dump. For this reason, it was suggested that, in order to refine the study area, a modem, organized storage system must be used instead of wild storage system in storing the urban wastes, and recyclable products must be used in the industry