In this article, a time dependent partial differential equation is used to model the nonlinear boundary value problem describing heat transfer through a radial porous Moving fin with rectangular profile. The study is performed by applying a numerical solver in MATLAB (pdepe), which is a centered finite difference scheme. The thermal conductivity and fin surface emissivity are linearly dependent on temperature while the heat transfer coefficient is given by power law function of temperature. The effects of thermophysical parameters, such as the Peclet number, surface emissivity coefficient, power index of heat transfer coefficient, convective-conductive parameter, radiative-conductive parameter and non-dimensional ambient temperature on temperature are studied.

Propagation of shock waves over a cylinder, sphere and projectile are numerically simulated. Time dependent full Reynolds averaged Navier-Stokes equations are solved numerically with Roe’s scheme. For cylinder and sphere, the diffraction pattern, loci of triple points and shape of diffraction shocks are obtained and compared with experimental results. It is shown that good agreement is obtained, and Roe’s method is capable of predicting those flows. Interaction of a Moving shock wave with flow around a SOCBT projectile is simulated numerically and flow features, pressure coefficient distribution on the projectile surfaces and the time histories of the drag force are obtained. Results show that as the Moving shock wave passes through the projectile, the flow field and aerodynamic forces are changed dramatically. The time history of the drag force shows that it decreases and even becomes negative while shock wave passes the projectile.

Taking the electric eel as a bionic object, a long undulatory fin is designed. The turbulent model standard k-ε is used to solve the N‒S equation of a three-dimensional unsteady incompressible fluid. The hydrodynamic characteristics of the undulatory fin are studied, and the influence of the swing angle, wave frequency and ground effects on the propulsion performance of the undulatory fin are discussed. The mathematical models of the average thrust and average lateral force of the undulatory fin are established by using multiple linear regression. The results show that the thrust and lateral force of the undulatory fin increase with increasing swing angle and swing frequency, but in a motion period, the number of fluctuations of the thrust is approximately twice that of the lateral force. The relationship between the average thrust force and the average lateral force of the undulatory fin and the wave frequency and the maximum swing angle satisfies a specific exponential law. When the undulating fin moves near the wall (d ≤0. 2 W), due to the coupling between the vortex at the lower edge and the tail vortex where part of the vortex is transferred to the two sides, the total thrust decreases, and the lateral force increases.

Precursors as informer pioneers of near future occurrence of earthquakes, are very diverse in their natures. We examined three short term possible precursors contain foreshocks, b-value variations, and amplitude abnormalities in the Very Low Frequency (VLF) radio signals for the November 14, 2021 fin double-earthquakes (M > 6). By searching-zoom method in earthquakes one degree on each side of the hypocenter location in the Iranian Seismological Center (IrSC), the International Earthquake Engineering and Seismology (IIEES) and the Building and Hosing Research Center (BHRC) catalogs, those data for the reviewing foreshocks were provided, then they analyzed by use of ZMAP for the b-value changes based on the Guttenberg-Richter empirical relation methodology. Whereas, in the BHRC accelerometer portal reported 8 events before the main shock times, none of them are not in the other catalogs. The temporal b-value variations from the normal, shown non sharp fits to the rises or falls of the seismicity as an expected indicator. Some b-value in accordance with the seismic up and down rate tracks, have high spatial uncertainties. We observed some amplitude anomalies in the VLF received signals from mean standard deviation in VLF signal measurements (2σ criterion in the statistical method) in about 4 days before and up to 5 days after the main shocks. Albeit, in follow the null hypothesis, for verifying (and not refused) these relations, are needed to be qualified data. As you will see, all three catalogs used in the coverage, quality, verification and appropriate data for logical and reliable review and processing are not less error than the expected standards. The main goal has been to investigate the possible precursors before the 2021 fin doublet earthquakes by using available local ground base data and obtainable facilities in this field and considering their improvement. The possibility of some foreshocks associated with double earthquakes cannot be ruled out. Therefore, the reliability of the studied precursors completely dependent to the proper data, that sufficient-precise instruments for their observations and recording are vital requirement. It is possible to use that kind of reliable and high-quality data in the analysis of pre-earthquake signals or even reasonable forecasting, which, if possible, will bring a valuable achievement in the future. We came to the conclusion that with such researches, the necessity of data quality and improving the level of their acquisition/standard in the country's research centers, must be carefully defined for more scientific and practical effects.