1,109 research outputs found
Controlling the onset of turbulence by streamwise traveling waves. Part 2. Direct numerical simulations
This work builds on and confirms the theoretical findings of Part 1 of this
paper, Moarref & Jovanovi\'c (2010). We use direct numerical simulations of the
Navier-Stokes equations to assess the efficacy of blowing and suction in the
form of streamwise traveling waves for controlling the onset of turbulence in a
channel flow. We highlight the effects of the modified base flow on the
dynamics of velocity fluctuations and net power balance. Our simulations verify
the theoretical predictions of Part 1 that the upstream traveling waves promote
turbulence even when the uncontrolled flow stays laminar. On the other hand,
the downstream traveling waves with parameters selected in Part 1 are capable
of reducing the fluctuations' kinetic energy, thereby maintaining the laminar
flow. In flows driven by a fixed pressure gradient, a positive net efficiency
as large as 25 % relative to the uncontrolled turbulent flow can be achieved
with downstream waves. Furthermore, we show that these waves can also
relaminarize fully developed turbulent flows at low Reynolds numbers. We
conclude that the theory developed in Part 1 for the linearized flow equations
with uncertainty has considerable ability to predict full-scale phenomena.Comment: To appear in J. Fluid Mec
Masses of constituent quarks confined in open bottom hadrons
We apply color-spin and flavor-spin quark-quark interactions to the meson and
baryon constituent quarks, and calculate constituent quark masses, as well as
the coupling constants of these interactions. The main goal of this paper was
to determine constituent quark masses from light and open bottom hadron masses,
using the fitting method we have developed and clustering of hadron groups. We
use color-spin Fermi-Breit (FB) and flavor-spin Glozman-Riska (GR) hyperfine
interaction (HFI) to determine constituent quark masses (especially quark
mass). Another aim was to discern between the FB and GR HFI because our
previous findings had indicated that both interactions were satisfactory. Our
improved fitting procedure of constituent quark masses showed that on average
color-spin (Fermi-Breit) hyperfine interaction yields better fits. The method
also shows the way how the constituent quark masses and the strength of the
interaction constants appear in different hadron environments.Comment: 15 pages, 6 tables, 1 figure. Accepted for publication in Mod. Phys.
Lett.
- …