Study of Available Turbulence and Cavitation Models to Reproduce Flow Patterns in Confined Flows

Abstract

Cavitating flow in nozzles is a complex flow which implies a highly turbulent two-phase one. An accurate simulation which improves some numerical results found in the literature was achieved by means of an extensive analysis of the capabilities of several numerical models for turbulence and cavitation. The analysis performed involves calibration/optimization tasks based on the physics of this kind of flow. This work aims to provide a quantitative criterion for the judgment of internal flow state, because it was demonstrated that the numerical results obtained with noncalibrated models could be enhanced by means of a careful calibration and thus saving computational costs.

Effect of Dissolved Carbon Dioxide on Cavitation in a Circular Orifice

“…Similar observations were also made by Singhal et al [30] and Lifante and Frank [44]. Darbandi et al [42] and Coussirat et al [46], using the cavitation model by Singhal et al [30] and a k-ω and SST k-ω turbulence model, respectively, do not find this overprediction; however, their C d values at higher cavitation numbers are underpredicted.…”

“…Similar observations were also made by Singhal et al [30] and Lifante and Frank [44]. Darbandi et al [42] and Coussirat et al [46], using the cavitation model by Singhal et al [30] and a k-ω and SST k-ω turbulence model, respectively, do not find this overprediction; however, their 𝐶 values at higher cavitation numbers are underpredicted. Figure 16 shows a comparison of the orifice discharge coefficients C d predicted using our CFD simulations for the three considered dissolved gas contents (i.e., GC1, GC2, and GC3) with those obtained from our experiments (see also Figure 13).…”

“…These limitations include: (1) no slip between the phases based on the homogenous mixture assumption, (2) thermodynamic relations for the phase mixture are not considered within the employed (R-P equation-based) liquid-vapor mass transfer model, (3) cavitation-induced gas release is not captured, since only pure vapor and gas bubbles are being modelled, (4) gas desorption and absorption is modeled ad hoc based on the difference between local partial gas pressure and its equilibrium pressure based on the amount of dissolved gas, and ( 5) the critical pressure of the liquid is set to equal its vapor pressure without considering the influence of viscous normal stresses. To demonstrate the consistency of our numerical results with prior numerical work on this specific orifice geometry, Figure 15 also includes results presented by Coussirat et al [46] based on a SST k-ω turbulence model and the cavitation model by Singhal et al [30] calibrated for this flow configuration. Note that Coussirat et al did not find meaningful differences in their results when using the Singhal et al [30] and the Zwart-Gerber-Belamri model [29].…”

“…As part of an investigation on cavitating aircraft ejector pumps, Mehring [12] also analyzed Nurick's Lucite nozzle geometry for both water and jet-A, both with dissolved air in the liquid phase (based on equilibrium conditions) and free air in the form of bubble nuclei in the upstream flow. Later, Coussirat et al [46] also studied this orifice geometry using ANSYS Fluent with a focus on the effect of different turbulence models, their calibration and by employing the Zwart-Gerber-Belamri model [29] and Singhal et al [30] model.…”

“…Effects of varying the amount of dissolved gas in the flow were not investigated in any of the prescribed investigations based on Nurick's nozzle geometry, even though Coussirat et al [46] considered small amounts of dissolved gases for calibrating their model(s). To the authors' knowledge, Coussirat et al were also the only ones to compare, aside from the predictions for the discharge coefficient, predicted local wall-pressure data with the respective data measured by Nurick.…”