Turbulence models have long been developed and examined for their accuracy and stability in variety of environments. While many flows work with excited turbulence intensity, models have rarely been tested to explore whether their accuracy withstands with augmented free stream turbulence intensity or decline in reasonable solutions. In present study the turbulent intensity of the air, moving parallel to a flat plate is increased from 0.4 to 6.6% for the whole flow, downstream to the screen. Three popular turbulence models are examined by investigating the turbulence penetration into flow field as well as into turbulent boundary layers over the flat plate. Results of numerical solutions for Standard k-e, Realizable k-e and finally two equations Shear Stress Transport k-w model are compared to experimental measurements and results are discussed. Results of variation of free stream turbulence intensity from flow field out of boundary layer, in addition, streamwise mean velocity, streamwise rms velocity and skin friction coefficient from boundary layer are investigated. Conclusion is made that despite restrictions of these turbulent models specially in predicting flow near a turbulent/non-turbulent interface, they have acceptable performance in both low and high intensity turbulent flows.

Sea surface brightness spectral anomalies from a Honolulu municipal outfall have been detected from space satellites in 200 km2 areas extending 20 km from the wastewater diffuser (Leung and Gibson 2004, Bondur 2005, Keeler et al. 2005, Gibson et al. 2006). Dropsonde and towed body microstructure measurements show greatly enhanced viscous and temperature dissipation rates above the outfall trapping-layer. Fossil-turbulence waves (FTWs) and secondary zombie-turbulence-waves (ZTWs) break as they propagate near-vertically and then break again near the surface to produce wind-ripple smoothing with narrow-wavelength l patterns from the soliton-like internal waves that supply turbulence energy to advected outfall fossils and to the ZTWs they radiate. The l= 30-250 m solitons reflect an efficient maser-action conversion of horizontal tidal and current kinetic energy by bottom boundary layer turbulence events to near-vertical FTWs with l the Ozmidov scak of the events at fossilization. Secondary (zombie) turbulence amplifies, channels in chinmeys, and near-vertically beams ambient internal wave energy at scales l just as energized metastable molecules amplify and beam quantum wavelengths in astrophysical lasers and masers around stars. Kilowatts of buoyancy power from the treatment plant produce fossil turbulence patches trapped below the thermocline. Beamed zombie turbulence maser action (BZTMA) in mixing chinmeys amplifies these kilowatts into the megawatts of surface turbulence dissipation required to affect brightness on wide sea surface areas. The BZTMA vertical mixing mechanism appears critical to vertical oceanic transport of information, heat, mass and momentum, and to the conversion of barotropic tides to baroclinic tides.

In the current study, after validating the accuracy of the current solution, mixed convection heat transfer in a square enclosure for drilling mudas a non-Newtonian fluidand wateras a Newtonian fluid—is investigated by finite volume method. The turbulence methods used in this study are the reliable methods such as RNG, standard, and RSM. The outcome of the investigation implies that under natural convection conditions, velocity boundary layer is somewhat asymmetrical on the cold wall and the fluid at the center of enclosure remains stratified and still. The existing graphs also indicate that the turbulence intensity is higher for forced convection than natural convection. Also, the maximum turbulence intensity is greater for drilling mud than water. One of the most prominent outcomes to be named is that, under similar circumstances, the Nusselt number for water is far more than the one for drilling mud, which confirms that convection heat transfer is greater in the water than the drilling mud.

There are many approaches to determine the sound propagated from turbulent flows. In hybrid methods, the turbulent noise source field is computed or modeled separately from the far-field calculations. To have an initial and quick estimation of the sound propagation, less computationally intensive methods can be developed using stochastic models of the turbulent fluctuations. In this paper, turbulent mean flow of a two dimensional, compressible, cold-jet at Mach 0.56 is computed using RANS with 2 equation k-e RNG model. The above mean-flow quantities are then used in a stochastic model to generate the details of the turbulent velocity fluctuations. This method is based on the use of classical Langevin equation to model the details of fluctuating flow field superimposed on the averaged computed quantities. The resulting sound field due to the generated unsteady flow is then evaluated using Lighthill's acoustic analogy. Our results are validated by comparing the directivity and the overall sound pressure level (OASPL) magnitudes with the available experimental data. Numerical results show reasonable agreement with the experiments, both in maximum directivity and the magnitude of the OASPL.

This study was carried out using two sets of numerical weather forecast data and flight reports for Clear Air Turbulence (CAT) over Iranian Plato to find atmospheric flow patterns favorable to the formation of CAT. The numerical data include five months of AVN analysis with horizontal resolution of 1 degree (about 100 km) and four months forecast data of MM5 model with resolution of 50 km. Important indices associated with conditions favorable for CAT formation include wind shear, flow deformation fields and atmospheric static stability (or joint effects such as Richardson number). These indices were estimated and also some algorithms such as Dutton to find their threshold values for CAT occurrence. The best selected algorithms are determined in the 5 months period using A VN outputs. In another 4 months period the MM5 outputs were used for the forecast of CAT using the POD method. The results for these periods indicated that severe CAT rarely occurred over Iran and condition for moderate CAT are often in upstream of troughs and ridges, near straight jet stream with cold advection and upper region of ridges. The POD method shows Dutton and Ellrod-2 are the best selected algorithms for CAT forecasting and have good consistency with observations. Their typical threshold values (associated with wind shears) are about 3 S-2 and 20 for moderated CAT respectively.

The present study investigates the turbulence characteristic of turbidity current experimentally. The three-dimensional Acoustic-Doppler Velocimeter (ADV) was used to measure the instantaneous velocity and characteristics of the turbulent flow. The experiments were conducted in a three-dimensional channel for different discharge flows, concentrations, and bed slopes. Results are expressed at various distances from the inlet, for all flow rates, slopes and concentrations as the distribution of turbulence energy, Reynolds stress and the turbulent intensity. It was concluded that the maximum turbulence intensity happens in both the interface and near the wall. Also, it was observed that the turbulence intensity reaches its minimum where maximum velocity occurs.