Hydraulic engineers have been interested in studying about "The Rate of Erodible Bed Scouring and its Development due to Jet Impacts". In this research it was investigated the changes of a jet down stream bed in two conditions of submerged & falling with applied discharge changes. Calvert outlet in submerged condition is exactly tangency on material bed level and in falling condition has 46 Cm distant from it. Tail water path in all of tests was constant and equal to 15 Cm. The jets in both two conditions make a 10 degree angle by horizon. The results indicated in early minutes of test the changes of scouring were severe but by passing time the changes in both two conditions are reduced. Hence, in submerged condition approximately 80% of final depth appears in early 5 minutes but in falling condition the rate is 70%.

In this study we review solar chromospheric jets and characteristics of them. The chromosphere and transition region are the interface between the solar photosphere and the corona, which plays a key role in the formation and acceleration of the solar wind. In recent years, scientists have made great efforts to understand the mechanism of energy transfer in the solar chromosphere and corona. The researchers suggest that the key to solving this problem may lie in understanding the nature of the small-scale transient events that are distributed across the surface of the Sun. Of these, solar spicules are the most prominent small-scale dynamical phenomena in the chromospheric regions that drive relatively cold material from the lower chromosphere to the corona. Spicules can heat the corona both by ejecting hot plasma and by energy transfer by magnetohydrodynamic (MHD) waves. These dynamical structures are formed when photospheric oscillations and convective flow along the magnetic field lines penetrate into the chromosphere.

In this paper, formation and development of one of the most dominant vortex structures, namely, counterrotating vortex pair (CVP) which is seen in the jet in cross flow are investigated numerically. Influences of the inclination angles between the nozzle (s) and channel on the CVP are presented for three inclination angles, a=30o, 60o and 90o at velocity ratio, R=2.0. Effects of the number of the nozzles on the evolution of CVP is analyzed by considering the single and three side-by-side positioned circular nozzles. In addition to the CVP, some secondary vortices are also reported by considered relatively a narrow channel because their existence cannot be showed in wider channel. Simulations reveal that higher the inclination angle the more jet penetration into the channel in all directions and increasing the inclination angle causes larger CVPs in size.Although the flow structure of the CVP formed in the single and three side-by-side nozzles are similar their evolution is quite different.

Various chromosphere and transition region jet-like structures abound playing an essential role in the dynamics and evolution therein. Tentatively identifying the wave characteristics and oscillatory behavior in the outer solar atmosphere helps to understand this layer better. In addition to the whip-like behavior, null-point motions in the reconnection site can excite transversal oscillation along the magnetical dense Jets, which is called the kink mode wave, and also this mode can evolve into Alfven wave after its propagation into the more homogeneous medium. The study of X-ray jets is an important topic in understanding the heating of the solar corona and the origin of the fast wind. The recently launched Hinode mission permitted us to observe the excellent proxies of these jets with an unprecedented high spatial resolution of 120 km on the Sun. We selected a high cadence sequence of SOT (Hinode) observations taken with both the HCaII and the Halpha filter to look at the details of the dynamics revealed by a significant jet event. Both wavelet and amplitude spectra analysis were used to analyze the observed kink wave and the time variations of intensities during the event. The results are discussed in the frame of different models implying reconnections with the inference of the dynamical phenomena occurring near several null points, including the oscillatory behavior.

The aim is to study nonlinear wave dynamics in solar spicules and jets. The life of jets in the context of Alfven wave dynamics is focused. Here, further insight into the solar atmospheric effects together with initial conditions on the dynamics of Alfven waves along with the characteristic parameters of the spicule or jet itself are provided. Results are based on the theory of magnetohydrodynamics. the location of shock formation by the interplay of the internal and external plasma-beta conditions together with the initial steady flow speeds which are rooted in the initiation location of the solar jet are illustrated. It was known that the plasma-beta of a solar jet affects the shock formation time of torsional Alfven waves. However, its efficiency is shown to be dependent on the external plasma beta conditions. The shock formation time for plasma-beta conditions over unity is directly proportional to the plasma-beta, similar to plasma-beta conditions equal to or below unity. In the case where the plasma-beta inside the magnetic structure is small, the shock formation time is accelerated by increasing the external plasma-beta. In photospheric conditions, as for coronal conditions, the time of shock formation is inversely proportional to the external plasma-beta. When the internal plasma-beta is fixed, for various steady flow speeds, the external plasma-beta accelerates the formation of shocks. These results help us to better understand the role of Alfven waves in solar jets in the transfer of energy to the solar system.

In this paper the results of 63 experiments about the inclination wall jets are presented. The angle of the jets changed from 0 to 20 degree and the densimetric Froude number of the jet change between 3.9 to 12.8. the tailwater ratio changed between 1.5 to 19. The scour mechanism due to 3D inclined wall jets is investigated. The effect of the jet angle for different values of the tailwater depth ratio and different values of the densimetric Froude number of the jets are studied. By using the densimetric Froude number of the jets, tailwater depth ratio and jet angle appropriate equations for estimating the scour hole dimensions are presented. The results show that by increasing the tailwater depth ratio decreasing of the dimensions of the jets are increased. There is a critical tailwater depth that beyond which by increasing or decreasing the tailwater depth the scour hole depth increases. The critical tailwater depth is increased by increasing the jet angle. In general the scour hole dimensions decreases by increasing the jet angle. Therefore, the inclined jets can be used as a procedure for decreasing the scour hole dimensions.