We perform numerical experiments on supernova-driven turbulent flows in order to see whether or not supernovae playa major role in driving turbulence in the interstellar medium. In a (200pc)3 computational box, we set up, as initial conditions, uniformly magnetized gas distributions with different pairs of hydrogen number densities and magnetic field strengths, which cover the observed values in the Galactic midplane. We then explode supernovae at randomly chosen positions at a Galactic explosion rate and follow up the evolution of the supernova-driven turbulent flows by integrating numerically the ideal MHD equations with cooling and heating terms. From the numerical experiments we find that the density-weighted velocity dispersions of the flows are in the range of 5-10 km s-l, which are consistent with the observed velocity dispersions of cold and warm neutral media. Additionally, we find that strong compressible flows driven by supernova explosions quickly change into solenoidal flows.

The imaging spectroscopic observations of the Magellanic irregular galaxy NGC 4449 were made to show the detailed kinematic structure of the galaxy. Many filamentary structures and Several bubble-like structures are recognized in a 3D data cube of H$\alpha$ 수식 이미지 emission line. Velocity field shows the kpc-scale mosaic structure and counter- rotation of ionized gas.

While the assessment of mean flow field is very important to characterize the hydrodynamic aspect of the flow regime in river, the conventional methodologies have required very time-consuming efforts and cost to obtain the mean flow field. The paper provides an efficient technique to quickly assess mean flow field by developing and applying spatial averaging method utilizing repeatedly surveyed acoustic Doppler current profiler(ADCP)’s cross-sectional measurements. ADCP has been widely used in measuring the detailed velocity and discharge in the last two decades. In order to validate the proposed spatial averaging method, the averaged velocity filed using the spatial averaging was compared with the bench-mark data computed by the time-averaging of the consistent fix-point ADCP measurement, which has been known as a valid but a bit inefficient way to obtain mean velocity field. The comparison showed a good agreement between two methods, which indicates that the spatial averaging method is able to be used as a surrogate way to assess the mean flow field. Bed shear stress distribution, which is a derived hydrodynamic quantity from the mean velocity field, was additionally computed by using both spatial and time-averaging methods, and they were compared each other so as to validate the spatial averaging method. This comparison also gave a good agreement. Therefore, such comparisons proved the validity of the spatial averaging to quickly assess mean flow field. The mean velocity field and its derived riverine quantities can be actively used for characterizing the flow dynamics as well as potentially applicable for validating numerical simulations.

A least-square regression analysis is applied for the estimation of velocity streamfunction field based on discretely sampled current meter data. The coefficients of a streamfunction that is expanded in terms of trigonometric basis function are obtained by enforcing the horizontal non-divergence of two-dimensional flow field. This method avoids interpolation and gives a root-mean-square (rms) residual of fit which includes the divergent part and noisiness of oceanic data. The implementation of the method is done by employing a boundaryfitted, curvilinear orthogonal coordinate which facilitates the specification of boundary conditions. An application is successfully made to the Texas-Louisiana shelf using the 32 months current meter data (31 moorings) observed as a part of the Texas-Louisiana Shelf and Transport Processes Study (LATEX). The rms residual of the fitting is relatively small for the shelf, which indicates the field is well represented by the streamfunction.

An objective method for the generation of velocity streamfunction is presented for dealing with discretely sampled oceanic data. The method treats a Poisson equation (forced by vorticity) derived from Helmholtz theorem in which streamfunction is obtained by isolating the non-divergent part of the two-dimensional flow field. With a mixed boundary condition and vorticity field estimated from observed field, the method is implemented over the Texas-Louisiana shelf based on the current meter data of the Texas-Louisiana Shelf Circulation and Transport Processes Study (LATEX) measured at 31 moorings for 32 months (April 1992 - November 1994). The resulting streamfunction pattern is quite consistent with observations. The streamfunction field by this method presents an opportunity to initialize and to verify computer models for local forecasts of environmental flow conditions for oil spill, nutrient and plankton transports as well as opportunity to understand shelf-wide low-frequency currents.