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This study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ω turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.
This study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ω turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.
Abraham JP, Sparrow EM, Gorman JM, et al. (2019). Application of an intermittency model for laminar, transitional, and turbulent internal flows. Journal of Fluids Engineering, 141: 071204.
Ai ZT, Mak CM (2013). Pressure losses across multiple fittings in ventilation ducts. Scientific World Journal, 2013: 195763.
Argyropoulos CD, Markatos NC (2015). Recent advances on the numerical modelling of turbulent flows. Applied Mathematical Modelling, 39: 693–732.
Arolla SK, Durbin PA (2013). Modeling rotation and curvature effects within scalar eddy viscosity model framework. International Journal of Heat and Fluid Flow, 39: 78–89.
Billard F, Laurence D (2012). A robust elliptic blending turbulence model applied to near-wall, separated and buoyant flows. International Journal of Heat and Fluid Flow, 33: 45–58.
Biswas R and Durbin PA (2019). Assessment of viscosity models that incorporate lag parameter scaling. International Journal of Heat and Fluid Flow, 78: 108427.
Biswas R, Durbin PA, Medic G (2019). Development of an elliptic blending lag k-ω model. International Journal of Heat and Fluid Flow, 76: 26–39.
Bredberg J, Peng SH, Davidson L (2002). An improved k-ω turbulence model applied to recirculating flows. International Journal of Heat and Fluid Flow, 23: 731–743.
Davidson L (2003). Modification of the V2F model for computing the flow in a 3D wall jet. Turbulence, Heat and Mass Transfer, 4: 577–584.
Durbin PA (1991). Near-wall turbulence closure modeling without "damping functions". Theoretical and Computational Fluid Dynamics, 3: 1–13.
Durbin PA (2018). Some recent developments in turbulence closure modeling. Annual Review of Fluid Mechanics, 50: 77–103.
Gan G, Riffat SB (1999). Determination of energy loss characteristics of dampers. International Journal of Energy Research, 23: 61–69.
Gao R, Chen S, Zhao J, et al. (2016). Coupling effect of ventilation duct bend with different shapes and sizes. Building Simulation, 9: 311–318.
Gibson MM, Launder BE (1978). Ground effects on pressure fluctuations in the atmospheric boundary layer. Journal of Fluid Mechanics, 86: 491–511.
Hrenya CM, Bolio EJ, Chakrabarti D, et al. (1995). Comparison of low Reynolds number k-ε turbulence models in predicting fully developed pipe flow. Chemical Engineering Science, 50: 1923–1941.
Iacovides H, Launder BE, Li HY (1996). Application of a reflection-free DSM to turbulent flow and heat transfer in a square-sectioned U-bend. Experimental Thermal and Fluid Science, 13: 419–429.
Jones WP, Launder BE (1972). The prediction of laminarization with a two-equation model of turbulence. International Journal of Heat and Mass Transfer, 15: 301–314.
Kalpakli Vester A, Örlü R, Alfredsson PH (2016). Turbulent flows in curved pipes: Recent advances in experiments and simulations. Applied Mechanics Reviews, 68: 050802.
Karbon M, Sleiti AK (2020). Large-eddy simulation of the flow in Z-Shape duct. Cogent Engineering, 7: 1778349.
Koch P (2006). The influence of Reynolds Number and size effects on pressure loss factors of ductwork components. Building Services Engineering Research and Technology, 27: 261–283.
Leutheusser HJ (1984). Velocity distribution and skin friction resistance in rectangular ducts. Journal of Wind Engineering and Industrial Aerodynamics, 16: 315–327.
Liu W, Long Z, Chen Q (2012). A procedure for predicting pressure loss coefficients of duct fittings using computational fluid dynamics (RP-1493). HVAC & R Research, 18: 1168–1181.
Mangeon G, Benhamadouche S, Wald JF, et al. (2020). Extension to various thermal boundary conditions of the elliptic blending model for the turbulent heat flux and the temperature variance. Journal of Fluid Mechanics, 905: 1–34.
Manning A, Wilson J, Hanlon N, et al. (2013). Prediction of duct fitting losses using computational fluid dynamics. HVAC & R Research, 19: 400–411.
Menter FR (2009). Review of the shear-stress transport turbulence model experience from an industrial perspective. International Journal of Computational Fluid Dynamics, 23: 305–316.
Menter FR, Smirnov PE, Liu T, et al. (2015). A one-equation local correlation-based transition model. Flow, Turbulence and Combustion, 95: 583–619.
Moujaes SF, Deshmukh S (2006). Three-dimensional CFD predications and experimental comparison of pressure drop of some common pipe fittings in turbulent flow. Journal of Energy Engineering, 132: 61–66.
Patel VC, Rodi W, Scheuerer G (1985). Turbulence models for near-wall and low Reynolds number flows—A review. AIAA Journal, 23: 1308–1319.
Peng SH, Davidson L, Holmberg S (1997). A modified low-Reynolds-number k-ω model for recirculating flows. Journal of Fluids Engineering, 119: 867–875
Pirozzoli S, Modesti D, Orlandi P, et al. (2018). Turbulence and secondary motions in square duct flow. Journal of Fluid Mechanics, 840: 631–655.
Pruvost J, Legrand J, Legentilhomme P (2004). Numerical investigation of bend and torus flows, part Ⅰ: Effect of swirl motion on flow structure in U-bend. Chemical engineering science, 59: 3345–3357.
Revell AJ, Craft TJ, Laurence DR (2011). Turbulence modelling of unsteady turbulent flows using the stress strain lag model. Flow, Turbulence and Combustion, 86: 129–151.
Schultz MP, Flack KA (2013). Reynolds-number scaling of turbulent channel flow. Physics of Fluids, 25: 025104.
Shao L, Riffat SB (1995). Accuracy of CFD for predicting pressure losses in HVAC duct fittings. Applied Energy, 51: 233–248.
Sleiti AK, Zhai J, Idem S (2013). Computational fluid dynamics to predict duct fitting losses: Challenges and opportunities. HVAC & R Research, 19: 2–9.
Wilcox DC (1994). Simulation of transition with a two-equation turbulence model. AIAA Journal, 32: 247–255.
Wolfshtein M (1969). The velocity and temperature distribution in one-dimensional flow with turbulence augmentation and pressure gradient. International Journal of Heat and Mass Transfer, 12: 301–318.
Wu P, Feng Z, Cao, SJ (2018). Fast and accurate prediction of airflow and drag force for duct ventilation using wall-modeled large-eddy simulation. Building and Environment, 141: 226–235.
This work is funded by the German Federal Ministry for Economic Affairs and Energy in the framework of the research program LuftKonVerTeR/BMWi 03ET1606A.
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