Statistical behavior of wall-attached motions in open- and closed-channel flows via direct numerical simulation

Direct numerical simulations at two friction Reynolds numbers (550 and 1000) have been performed to explore the statistical behaviors of wall-attached motions (WAMs) in open- closed-channel flows (OCFs CCFs). To fully capture largest energetic WAMs, superlarge domain sizes are employed (24–48 π h along streamwise direction with being height OCFs). Based on analysis linear coherence spectrum, both geometric kinematic characteristics WAMs investigated. Results revealed that obvious peaks could be found spanwise spectra u (streamwise velocity) w (spanwise a wavelength close 2h. Both energy density value OCFs greater than those CCFs large wavelengths, indicating more wall-attached. Within y/h = 0.2–0.7, diagnosed wavelengths increase roughly linearly increasing vertical position y. In upper region ( y / > 0.7), smaller CCFs. addition, inclination angle fluctuates around 14° within 0.4–0.6, angles slightly larger when 0.6. Regarding behavior, contribution fractions total turbulent intensity always Additionally, were sensitive number w.