Valentin Boutrouche

Bio: Valentin Boutrouche is an academic researcher from University of Massachusetts Lowell. The author has contributed to research in topics: Hagen–Poiseuille equation & Turbulence. The author has an hindex of 2, co-authored 2 publications receiving 11 citations. Previous affiliations of Valentin Boutrouche include University of Pau and Pays de l'Adour.

Digitally manufactured air plasma-on-water reactor for nitrate production

Abstract: The sustainable production of food to support the increasing world population is one of humanity’s most pressing challenges. Plasma activated water, produced using renewable energy, can help fulfill plants’ needs in sustainable agriculture approaches. The design, implementation, and characterization of a digitally manufactured air plasma-on-water reactor (POWR) for the synthesis of nitrate as green nitrogen fertilizer is presented. The interaction of air plasma-generated reactive oxygen and nitrogen species with water produces nitrate (NO3 −) and related species, which are the main nitrogen-containing nutrients for plants. The mild conditions of the operation of the POWR opens the possibility to use plastics, particularly through digital manufacturing strategies such as 3D-printing, for its fabrication. A pin-to-plate reactor configuration powered by high-voltage alternating power is chosen due to its simplicity and efficacy. A computational thermal-fluid model is used to evaluate the design and attain expected operational characteristics. The experimental characterization of the POWR encompassed design and operation parameters, namely electrode-water spacing, air flow rate, and voltage level. A machine learning approach is implemented to extract and quantify characteristic features of the plasma–water interaction, such plasma volume and plasma–water interface area. Experimental results revealed that the nitrate production rate varies linearly with dimensionless plasma volume. The design, fabrication, and characterization methods presented can be adapted to other POWRs and help enable on-demand nitrogen fertilizer production at low environmental and economic cost.

Investigation of thermal large-eddy simulation approaches in a highly turbulent channel flow submitted to strong asymmetric heating

Abstract: This study deals with thermal large-eddy simulation (T-LES) of anisothermal turbulent channel flow in the working conditions of solar receivers used in concentrated solar power towers The flow is characterized by high-temperature levels and strong heat fluxes The hot and cold friction Reynolds numbers of the simulations are, respectively, 630 and 970 The Navier–Stokes equations are solved under the low-Mach number approximation and the thermal dilatation is taken into account The momentum convection and the density–velocity correlation subgrid terms are modeled Functional, structural, and mixed subgrid-scale models are investigated A tensorial version of the classical anisotropic minimum-dissipation (AMD) model is studied and produces good results A Quick scheme and a second-order-centered scheme are tested for the discretization of the mass convection term First, a global assessment of 22 large-eddy simulations is proposed, then six are selected for a careful analysis including profiles of mean quantities and fluctuation values as well as a comparison of instantaneous fields Probability density functions of wall heat fluxes are plotted The results point out that T-LESs performed with the Quick scheme tend to underestimate the wall heat flux whereas the second-order-centered scheme significantly improves its estimation T-LESs tend to overestimate the peaks of velocity correlations When regarding the dimensionless profiles of fluctuations, the tensorial AMD model provides better results than the other assessed models For the heat flux estimation, the best agreement is found with the AMD model combined with the second-order-centered scheme

Direct simulations and subgrid modeling of turbulent channel flows asymmetrically heated from both walls

Abstract: Thermal large-eddy simulations (T-LES) and a direct numerical simulation are carried out in a bi-periodical channel with hot and cold wall temperatures of, respectively, 900 and 1300 K. The mean fluid temperature is lowered below the cold wall temperature thanks to a heat source, resulting in a both walls heating of the fluid. The hot and cold wall friction Reynolds numbers are, respectively, 640 and 1000. These conditions are representative of the working conditions of gas-pressurized solar receiver of solar power tower. The low Mach number Navier–Stokes equations are solved. The coupling between the dynamic and the temperature effects is considered. In the T-LES, both the momentum convection and the density–velocity correlation subgrid terms are modeled. Functional models, structural models, and mixed models are considered. A tensorial version of the anisotropic minimum-dissipation (AMD) model is also investigated. The Quick and the second-order-centered schemes are tested for the discretization of the mass convection term. First, an overview of the results of 17 T-LES on first- and second-order statistics is proposed. It permits selecting 6 of these simulations for a detailed analysis consisting in the investigation of profiles of mean quantities and turbulent correlations. Particular attention is given to the wall heat fluxes because they are a critical point for the design and the optimization of solar receivers. Overall, the first-order statistics are better predicted than the second-order's. The tensorial AMD model takes advantage of the classical AMD model properties and better reproduces the anisotropy of the flow thanks to its formulation. The tensorial AMD model produces the most reliable and efficient results among the considered models.

Effect of heat-flux ratio on two-dimensional horizontal channel flow

Abstract: Numerical analysis is performed to investigate thermal fluid-flow transport phenomena in channel under asymmetrical heat flux from both side walls. Emphasis is placed on an effect of heat-flux ratio from both sides on the velocity and thermal fields. The low-Reynolds-number κ-e turbulence model and the two-equation heat-transfer model are employed to determine turbulent viscosity and thermal eddy diffusivity, respectively