Two-Phase Flow Effects on Seismic Wave Anelasticity in Anisotropic Poroelastic Media

We study the wave anelasticity (attenuation and velocity dispersion) of a periodic set of three flat porous layers saturated by two immiscible fluids. The fluids are very dissimilar in properties, namely gas, oil, and water, and, at most, three layers are required to study the problem from a general point of view. The sequence behaves as viscoelastic and transversely isotropic (VTI) at wavelengths much longer than the spatial period. Wave propagation causes fluid flow and slow P modes, inducing anelasticity. The fluids are characterized by capillary forces and relative permeabilities, which allow for the existence of two slow modes and the presence of dissipation, respectively. The methodology to study the physics is based on a finite-element uspcaling approach to compute the complex and frequency-dependent stiffnesses of the effective VTI medium. The results of the experiments indicate that there is higher dissipation and anisotropy compared to the widely used model based on an effective fluid that ignores the effects of surface tension (capillarity) and viscous flow interference between the two fluid phases.

Effect of Distortion in Velocity Profile on Flow Measurements Using Averaging Flow Sensors

This article reports the analysis on the flow interference due to the pressure-averaging probe. The disturbance in the velocity field generated by elbows with radii of curvature of 1D and 3D (D-internal diameter of a pipeline) were investigated based on the results recorded by selected probes with various cross-sections installed at distances in the range of 3D to 20D from the elbow. The uncertainty in the current measurement is 8.26% for a circular probe. The uncertainty was related to the distance between the probe and the elbow and the relative location of the elbow with respect to the probe. This uncertainty was found to significantly depend on the design of the cross-section of the probe. Unsteady RANS computations with the standard k-ω model are used in the current numerical approach. The distributions of the velocities and pressures of fluid flow in the vicinity of the probe were determined. Mathematical modeling can also provide guidance to improve and adapt the metrological properties of the flowmeter to the conditions of its place of installation.

Joint Channel and Interference Aware Cooperative Routing for Cognitive Radio Network

Cognitive Radio based network technology provides a promising solution for various types of real-time wireless communication by offering better spectrum utilization and resource allocation. Generally, the dynamic network topology, interference, channel switching and under-utilization of resource can degrade the network performance. Therefore, development of promising solution to obtain the desired performance is a challenging research topic in CRNs. Several researches have been carried out which have focused on development of routing protocol for CRNs to improve the performance. These routing protocols are classified as local and global routing which are mainly focused on overhead reduction and optimal route selection respectively. However, the conventional approaches suffer from various issues such as interflow-interference, channel switching delay and node overhearing problems which can progress towards the poor network performance. In this paper, our objective is to focus on the inter-flow interference, channel switching delay, and develop a cooperative communication based approaches where inter-flow interference and overhearing issues are mitigated using cooperative communication. Furthermore, Switching Delay and Interference (SDI) routing metric is developed to reduce the switching delay and also finally, a cooperative scheme of packet transmission is developed where direct or cooperative communication is selected for successful packet transmission. The proposed approach jointly considers channel and interference issue, hence it is known as Joint Cooperative Channel and Interference Aware Routing (JCIAR). The performance of proposed approach is compared with the existing techniques such as Primary User Aware k-hop route discovery scheme (PAK), AODV, CognitiveAODV, and Location-Aided Routing for CRN (LAUNCH) in terms of delay, packet delivery rate and throughput. The obtained result shows a significant improvement in network performance.

Flow Around Three Side-by-Side Square Cylinders and the Effect of the Cylinder Oscillation

In this study, the flow field over three square cylinders (SCs) arranged side by side is investigated in a low-speed wind tunnel. The experiments are performed with three similar SCs for Reynolds number (Re) 295. The influences of spacing ratio on the wake size, drag coefficient, and flow interference of the cylinders are reported with the hotwire anemometry, particle image velocimetry (PIV), and the flow visualization techniques. Special attention is paid to the oscillation given to the middle cylinder and its effect on flow structure and related forces. The spacing ratio (s/D) ranges from 1.5 to 3, whereas the forcing frequency ratio ranges from 0.5 to 2 with amplitude of 10% of the cylinder width. It is observed that the spacing influences the flow structure, and the vortex shedding mechanism strongly. A secondary frequency appears in the flow field for spacing ratio s/D = 2 and 3. Depending upon the spacing ratios, the flow pattern is seen to be asymmetric biased, symmetric biased, and weakly interactive. The wake interaction decreases with increase in spacing ratios. With the oscillations, the wake becomes more unstable and complex. Additional wake oscillation frequency appears in the power spectra. With an increase in spacing ratios, the drag coefficient decreases, whereas with oscillations, higher drag force is observed compared to a stationary cylinder. A correlation is developed between the time-averaged drag coefficient with cylinder spacing and Reynolds number.

Identifying the Design Alternatives and Flow Interference of Tuna Purse Seine by the Numerical Modelling Approach

Dynamic responses of tuna purse seine to currents were numerically studied with regard to the vertical subsidence and global load distribution, and determinant attributes were identified. We rebuilt the submerged geometry of a purse seine net using the lumped mass method with hydrodynamic coefficients obtained from measurements of the prototype material, as well as a mesh grouping method, which corrects the twine diameter and netting material density for the equivalent net by introducing the compensation coefficient. Uneven tension distribution showed that it was vulnerable to high loads in the bunt area at shooting and along the lead line at pursing. High loads were present at the convex sections of net circles in the direction of the current. Higher shooting speeds resulted in well-balanced sinking, while a reduced hanging ratio of netting panels was beneficial to faster sinking. While large mesh sizes reduce water resistance and increase sinking velocity, extensive use should be cautioned in terms of the sensibility to stress. Comparing two options of different proportions of large-mesh panels, mesh sizes doubled for 15 strips versus 5 strips, suggesting that the 15 strip option would pose a higher risk of strand vulnerability, while the 5 strip option may be a more balanced alternative with a lower mesh density and a lower mesh stress.