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Forooghi, Pourya Weidenlener, Alex Magagnato, Franco Böhm, Benjamin Kubach, Heiko Koch, Thomas and Frohnapfel, Bettina 2018. DNS of momentum and heat transfer over rough surfaces based on realistic combustion chamber deposit geometries. International Journal of Heat and Fluid Flow, Vol. 69, p. 83.
Mazzuoli, Marco and Uhlmann, Markus 2017. Direct numerical simulation of open-channel flow over a fully rough wall at moderate relative submergence. Journal of Fluid Mechanics, Vol. 824, p. 722.
Krumbein, Benjamin Forooghi, Pourya Jakirlić, Suad Magagnato, Franco and Frohnapfel, Bettina 2017. VLES Modeling of Flow Over Walls with Variably-shaped Roughness by Reference to Complementary DNS. Flow, Turbulence and Combustion, Vol. 99, Issue. 3-4, p. 685.
Rodi, Wolfgang 2017. Turbulence Modeling and Simulation in Hydraulics: A Historical Review. Journal of Hydraulic Engineering, Vol. 143, Issue. 5, p. 03117001.
Vowinckel, Bernhard Nikora, Vladimir Kempe, Tobias and Fröhlich, Jochen 2017. Momentum balance in flows over mobile granular beds: application of double-averaging methodology to DNS data. Journal of Hydraulic Research, Vol. 55, Issue. 2, p. 190.
Kidanemariam, Aman G. and Uhlmann, Markus 2017. Formation of sediment patterns in channel flow: minimal unstable systems and their temporal evolution. Journal of Fluid Mechanics, Vol. 818, p. 716.
Lee, Hyungoo and Balachandar, S. 2017. Effects of wall roughness on drag and lift forces of a particle at finite Reynolds number. International Journal of Multiphase Flow, Vol. 88, p. 116.
Ghodke, Chaitanya D. and Apte, Sourabh V. 2016. DNS study of particle-bed–turbulence interactions in an oscillatory wall-bounded flow. Journal of Fluid Mechanics, Vol. 792, p. 232.
Kuwata, Y. and Suga, K. 2016. Lattice Boltzmann direct numerical simulation of interface turbulence over porous and rough walls. International Journal of Heat and Fluid Flow, Vol. 61, p. 145.
Derksen, Jos J. 2015. Simulations of granular bed erosion due to a mildly turbulent shear flow. Journal of Hydraulic Research, Vol. 53, Issue. 5, p. 622.
Yuan, J. and Piomelli, U. 2015. Numerical simulation of a spatially developing accelerating boundary layer over roughness. Journal of Fluid Mechanics, Vol. 780, p. 192.
Chouippe, Agathe and Uhlmann, Markus 2015. Forcing homogeneous turbulence in direct numerical simulation of particulate flow with interface resolution and gravity. Physics of Fluids, Vol. 27, Issue. 12, p. 123301.
Hong, Anyu Tao, Mingjiang and Kudrolli, Arshad 2015. Onset of erosion of a granular bed in a channel driven by fluid flow. Physics of Fluids, Vol. 27, Issue. 1, p. 013301.
Kempe, Tobias Lennartz, Matthias Schwarz, Stephan and Fröhlich, Jochen 2015. Imposing the free-slip condition with a continuous forcing immersed boundary method. Journal of Computational Physics, Vol. 282, p. 183.
Vowinckel, Bernhard Kempe, Tobias and Fröhlich, Jochen 2014. Fluid–particle interaction in turbulent open channel flow with fully-resolved mobile beds. Advances in Water Resources, Vol. 72, p. 32.
Ji, Chunning Munjiza, Ante Avital, Eldad Xu, Dong and Williams, John 2014. Saltation of particles in turbulent channel flow. Physical Review E, Vol. 89, Issue. 5,
Uhlmann, Markus and Doychev, Todor 2014. Sedimentation of a dilute suspension of rigid spheres at intermediate Galileo numbers: the effect of clustering upon the particle motion. Journal of Fluid Mechanics, Vol. 752, p. 310.
Ji, ChunNing Ante, Munjiza Eldad, Avital Xu, Dong and John, Williams 2014. Numerical investigation of particle saltation in the bed-load regime. Science China Technological Sciences, Vol. 57, Issue. 8, p. 1500.
Stoesser, Thorsten 2014. Large-eddy simulation in hydraulics: Quo Vadis?. Journal of Hydraulic Research, Vol. 52, Issue. 4, p. 441.
Kidanemariam, Aman G. and Uhlmann, Markus 2014. Interface-resolved direct numerical simulation of the erosion of a sediment bed sheared by laminar channel flow. International Journal of Multiphase Flow, Vol. 67, p. 174.
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Direct numerical simulation of open channel flow over a geometrically rough wall has been performed at a bulk Reynolds number of . The wall consisted of a layer of spheres in a square arrangement. Two cases have been considered. In the first case the spheres are small (with diameter equivalent to wall units) and the limit of the hydraulically smooth flow regime is approached. In the second case the spheres are more than three times larger ( wall units) and the flow is in the transitionally rough flow regime. Special emphasis is given to the characterisation of the force and torque acting on a particle due to the turbulent flow. It is found that in both cases the mean drag, lift and spanwise torque are to a large extent produced at the top region of the particle surface. The intensity of the particle force fluctuations is significantly larger in the large-sphere case, while the trend differs for the fluctuations of the individual components of the torque. A simplified model is used to show that the torque fluctuations might be explained by the spheres acting as a filter with respect to the size of the flow scales which can effectively generate torque fluctuations. Fluctuations of both force and torque are found to exhibit strongly non-Gaussian probability density functions with particularly long tails, an effect which is more pronounced in the small-sphere case. Some implications of the present results for sediment erosion are briefly discussed.
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