Double-averaged kinetic energy budgets in flows over mobile granular beds: insights from DNS data analysis. Issue 4 (6th June 2020)

• Record Type: Journal Article
• Authors: Papadopoulos, Konstantinos; Nikora, Vladimir; Vowinckel, Bernhard; Cameron, Stuart; Jain, Ramandeep; Stewart, Mark; Gibbins, Christopher; Fröhlich, Jochen
• Is Part Of: Journal of hydraulic research. Volume 58:Issue 4(2020)
• Page Start: 653
• Page End: 672
• Publication Date: 2020-06-06
• Subjects: Double-averaging methodology -- flow–sediment interactions -- mean kinetic energy balance -- mobile-granular beds -- turbulent kinetic energy -- turbulent open-channel flows; Hydraulics -- Research -- Periodicals; Hydraulic engineering -- Periodicals; Hydraulic engineering; Electronic journals; Periodicals; 621.2
• DOI: 10.1080/00221686.2019.1661291
• Languages: English
• ISSNs: 0022-1686

Abstract

Abstract : The equations for double-mean, form-induced and spatially averaged turbulent energy budgets are employed to analyse data from direct numerical simulations of turbulent open-channel flows over transitionally rough mobile beds with intermediate flow submergence. Two scenarios were considered related to (i) near-critical bed condition, and (ii) fully mobile bed condition. The bed was composed of a layer of mobile spherical particles moving on the top of one layer of fixed particles of the same size. Data analysis showed the leading energy exchanges between double-mean, form-induced, turbulent flow field contributions as well as particle motions. Above the fixed particles tops, the turbulent flow receives kinetic energy directly from the mean flow as well as from moving bed particles, which in turn also receive energy from the mean flow. For near-critical bed condition, particle aggregations enhanced mean-flow heterogeneity, strengthened turbulent stresses and their effects on the flow, while at increased bed-mobility, energy transport mechanisms became weaker and conversions induced by viscous stresses and pressure became stronger.