This study aims to quantify how turbulence in a channel flow mixes momentum in the mean sense. We applied the macroscopic forcing method to direct numerical simulation (DNS) of a turbulent channel flow at Re$_\tau$=180 using two different forcing strategies that are designed to separately assess the anisotropy and nonlocality of momentum mixing. In the first strategy, the leading term of the Kramers-Moyal expansion of the eddy viscosity operator is quantified where the macroscopic forcing is employed to reveal all 81 tensorial coefficients that essentially represent the local-limit eddy viscosity. The results indicate: (1) eddy viscosity has significant anisotropy, (2) Reynolds stresses are generated by both mean strain rate and mean rotation rate tensors, and (3) the local-limit eddy viscosity generates asymmetric Reynolds stress tensors. In the second strategy, the eddy viscosity operator is considered as an integration kernel representing the nonlocal influence of mean gradients on the Reynolds stresses. Considering the average of this kernel in the homogeneous directions, the macroscopic forcing is designed to reveal the nonlocal effects in the wall-normal direction for all 9 components of the Reynolds stresses. Our results indicate that while the shear component of the Reynolds stress is reasonably controlled by the local mean gradients, other components of the Reynolds stress are highly nonlocal. These two analyses provide accurate verification data for quantitative testing of anisotropy and nonlocality effects in turbulence closure models. Comment: 37 pages, 24 figures
Nawaf Almutairi, Ahamd Alanazi, Mohammed Seyam, Faizan Zaffar Kashoo, Danah Alyahya, and Radhakrishnan Unnikrishnan
Bulletin of Faculty of Physical Therapy, Vol 27, Iss 1, Pp 1-8 (2022)
Core muscles strength, Dynamic balance, Hospital staff, Miscellaneous systems and treatments, and RZ409.7-999
Abstract Background Healthcare workers are at the risk of developing weakness in core muscles and balance disturbance due to stress at the workplace. The purpose of this study was to examine the relationship between core muscle strength measured with a plank test and dynamic balance assessed with the modified Star Excursion Balance Test (MSEBT) among hospital staff. A convenience sample of 27 healthy male employees at Rabigh General Hospital participated in the study; participants performed MSEBT and plank tests in the gym of the physical therapy department at the hospital. Results The mean age of the 27 participants was 32.19, standard deviation (SD) 4.16 years; mean height was 171.15, SD 6.39 cm; mean weight was 72.37, SD 11 kg; and body mass index was 24.73, SD 3.62 kg/m2. Pearson’s correlation coefficient showed a positive significant correlation between scores on the plank test with leg reach scores on MSEBT. The data showed a highest correlation between scores on plank test with dominant anterior leg reach scores on MSEBT (r = 0.446, p = 0.010), and lowest with non-dominant anterior leg reach scores on MSEBT (r = 0.335, p = 0.044). Conclusion Weak to moderate positive significant correlation between the plank test of isometric core muscle strength and both the right and dominant of the anterior, posteromedial, and composite score on the MSEBT of the lower limb and significantly with non-dominant anterior reach. There was no significant difference between the administrative and health practitioner on the plank test or MSEBT.