Velocity Layer Research Articles

Analysis of Reciprocal Thermal Conductivity on Free Convection Flow along a Wavy Vertical Surface

The effects of thermal conductivity which depend on temperature are conversely proportional with the linear function of temperature on free convective flow where the fluid is viscous and incompressible along a heated uniform and the vertical wavy surface has been examined in this study. The boundary layer equations with the associated boundary conditions that govern the flow are converted into a nondimensional form by using an appropriate transformation. In the domain of a vertical plate that is flat, the resulting method of nonlinear PDEs is mapped and then worked out numerically by applying the implicit central finite difference technique with Newton’s quasilinearization method, and the block Thomas algorithm is well known as the Keller-box method. The outputs are obtained in the terms of the heat transferring rate, the frictional coefficient of skin, the isotherms, and streamlines. The outcomes showed that the local heat transferring rate, the local skin friction coefficient, the temperature, and the velocity all are decreasing, and both the thermal layer of boundary and velocity become narrower with the rising values of reciprocal variation of temperature-dependent thermal conductivity. On the other hand, the friction coefficient of skin, the velocity, and the temperature decrease where the friction coefficient of skin and velocity decrease by 43% and 64%, respectively, but the heat transfer rate increases by 61% approximately, and both the boundary layer thermal and velocity become thinner when the Prandtl number increases.

Validation on the mean friction velocity of an atmospheric boundary layer flow reproduced by large-eddy simulation in terms of kinetic energy conservation

This study presents a validation of large-eddy simulation to reproduce normalized mean friction velocity in an atmospheric boundary layer flow in terms of kinetic energy conservation uncertainty. A primary finding of this study is that the normalised mean friction velocity of the atmospheric boundary layer is suggested to be insensitive to kinetic energy conservation errors. The present study approaches the sensitivity of the normalized friction velocity, which is one of the most fundamental statistics in the atmospheric boundary layer, to the uncertainty. The nearly complete conservation of kinetic energy in the present numerical framework is verified in an inviscid homogeneous isotropic fluctuation field. Then, the present analysis is applied to reproducing turbulent channel flows as direct numerical simulation and large-eddy simulation based on the previous studies before the present work analyses the present atmospheric boundary layer. The present analysis is then used to analyze the normalized friction velocity in the atmospheric boundary layer. The values of the friction velocity obtained in the previous study are in good agreement with that of the present study.

Thermal performance analysis and optimization of cascaded packed bed latent heat storage tank

The packed bed tank with multiple phase change materials (PCMs) is one of the most efficient latent heat energy storage techniques. This study presents insight into the influence of the latent heat arrangements on the cascaded packed bed tank, providing a new idea for designing multi-PCM packed bed tank, which concerns the screening of PCMs. In this study, a parametric study is conducted to optimize the latent heat of the multi-PCM packed bed tank for the charging and discharging process. A developed two-dimensional model is used to predict the thermal behaviors of the heat transfer fluid and PCMs in packed bed tanks, which is verified by experiment. The results showed that the case with uniform latent heat arrangement exhibits the best overall thermal performance, which obtains the lowest standard deviation of average heat-exchange zone travel velocities for the charging and discharging cycle process. Moreover, the relationship between the efficiency and the standard deviations of the heat-exchange-zone travel velocities is unearthed, and its effectiveness is verified by an actual cascaded PCMs packed bed tank. The charging/discharging/overall efficiency increases with a decrease in the standard deviation of the heat-exchange-zone travel velocities of the PCM layers. This relationship can be used as a new PCM selection method for the cascaded latent heat storage tank. In addition, the actual cascaded packed bed unit with a different latent heat is optimized by variable capsule diameters.

A machine learning approach for calibrating seismic interval velocity in 3D velocity model

Velocity model technique is routinely used to convert data from the time-to-depth domain to support prospect evaluation, reservoir modelling, well engineering, and further drilling operation. In Vietnam, the conventional velocity model building workflow oversimplifies the interval velocities as only well interval velocities are populated into 2D grids for depth conversion or oversimplified calibration interval velocities by applying a single scaling factor function. This study explores the 3D velocity model workflow to obtain accurate and high-resolution interval velocities using a machine learning approach for both fields A and B in Cuu Long basin, offshore Vietnam.
 To design an effective approach to depth conversion, the anisotropy factor analysis was performed to understand the differences between the seismic and well interval velocities in geological layer in the 3D structural model. The seismic interval velocity was multiplied by the anisotropy factor to achieve the scaling seismic interval velocity. The scaling seismic interval velocity, elastic attributes, geometric attributes, structural and stratigraphic attributes were used as training features (variables) for predicting interval velocity using the supervised learning algorithm in the machine learning model. Supervised learning offers an opportunity to develop an expert-knowledge-based automated system, which incorporates both domain knowledge and quantitative data mining [1]. The random forest regression algorithms were selected for predicting interval velocity after evaluating several machine learning algorithms. To provide insight into the uncertainty of final interval velocity, a depth uncertainty analysis was conducted using a blind well test for 24 wells and 7 horizons.
 The comprehensive 3D velocity model using machine learning approach was built for the first time in Cuu Long basin, offshore Vietnam. The result showed the machine learning algorithm can address the disadvantages of conventional velocity calibration to create highly accurate depth representations of the subsurface including a measure of the uncertainty.

Heat transportation performance and entropy generation analysis of Iron (II, III) oxide microparticles on Taylor Couette flow over a slit wall

Despite the significance of Taylor Couette flow over a slit wall in industries, little is known about the impact of Iron (II, III) oxide (Fe3O4) microparticle on the dynamics and heat transfer properties of Taylor-Couette flow. This study aims to investigate the effect of solid particles on heat transfer performance of Taylor-Couette flow over a slit wall. The trajectory of particles in the flow field is described utilizing Eulerian-Lagrangian method in this report. The Fe3O4-water suspension with particle size dp = 1μm, 5μm and particle volume fraction φ = 0.5 % , 1.0 % , 1.5% are considered. Results reveal that the heat transfer performance of Taylor vortex is remarkable enhanced by adding the solid particles inside the annular gap compared to pure water. Solid particles in the annular gap show the movement of migration from inner to outer cylinders due to the interaction with fluid, which causes more disordered flow field around the inner cylinder. The addition of particles could significantly thin the velocity and temperature boundary layers. Frictional and thermal entropy generation display a reverse tendency with increasing particle volume fraction and size. Thermal entropy generation appears obviously higher than frictional entropy generation. Suspension with φ = 1.5% and dp = 1μm makes optimal performance of Taylor vortex because of the minimum entropy generation and boundary layers.

A nanoparticle formation model considering layered motion based on an electrical explosion experiment with Al wires

To study the evolution of nanoparticles during Al wire electrical explosion, a nanoparticle formation model that considered layered motion was developed, and an experimental system was set up to carry out electrical explosion experiments using 0.1 mm and 0.2 mm Al wires. The characteristic parameters and evolution process during the formation of nanoparticles were calculated and analyzed. The results show that the maximum velocities of the innermost and outermost layers are about 1200 m·s−1 and 1600 m·s−1, and the velocity of the middle layer is about 1400 m·s−1, respectively. Most of the nanoparticles are formed in the temperature range of 2600 K‒2500 K. The characteristic temperature for the formation of Al nanoparticles is ∼2520 K, which is also the characteristic temperature of other parameters. The size distribution range of the formed nanoparticles is 18 to 110 nm, and most of them are around 22 nm. The variation of saturated vapor pressure determines the temperature distribution range of particle nucleation. There is a minimum critical diameter of particles (∼25 nm); particles smaller than the critical diameter can grow into larger particles during surface growth. Particle motion has an effect on the surface growth and aggregation process of particles, and also on the distribution area of larger-diameter particles. The simulation results are in good agreement with the experiments. We provide a method to estimate the size and distribution of nanoparticles, which is of great significance to understand the formation process of particles during the evolution of wire electrical explosion.

Influence of train roof boundary layer on the pantograph aerodynamic uplift: A proposal for a simplified evaluation method

The mean contact force between pantograph collectors and contact wire is affected by the aerodynamic uplift generated by aerodynamic forces acting on pantograph components. For a given pantograph geometry, orientation and working height, aerodynamic forces are strongly influenced by the position of the pantograph along the train roof, since an aerodynamic boundary layer grows along the train.This paper shows the experimental results of aerodynamic uplifts of full-scale pantographs located at four different positions along the roof of a high-speed train and adopts CFD simulations to examine the effect of the boundary layer velocity profile on the measured experimental forces. It is quantitatively demonstrated that the same pantograph located at different positions along the train roof can show relevant differences in the aerodynamic uplift, only due to the different flow characteristics.Moreover, a new simplified methodology is proposed to evaluate the aerodynamic uplifts at different positions of the pantograph along the train. Results of the proposed methodology are validated against full scale experimental results and full CFD simulations exploiting the complete model of the pantograph installed on the train roof.

Understanding surface wave modal content for high-resolution imaging of submarine sediments with distributed acoustic sensing

SUMMARY Ocean bottom distributed acoustic sensing (OBDAS) is emerging as a new measurement method providing dense, high-fidelity and broad-band seismic observations from fibre-optic cables deployed offshore. In this study, we focus on 35.7 km of a linear telecommunication cable located offshore the Sanriku region, Japan, and apply seismic interferometry to obtain a high-resolution 2-D shear wave velocity (VS) model below the cable. We first show that the processing steps applied to 13 d of continuous data prior to computing cross-correlation functions (CCFs) impact the modal content of surface waves. Continuous data pre-processed with 1-bit normalization allow us to retrieve dispersion images with high Scholte-wave energy between 0.5 and 5 Hz, whereas spatial aliasing dominates dispersion images above 3 Hz for non-1-bit CCFs. Moreover, the number of receiver channels considered to compute dispersion images also greatly affects the resolution of extracted surface-wave modes. To better understand the remarkably rich modal nature of OBDAS data (i.e. up to 30 higher modes in some regions), we simulate Scholte-wave dispersion curves for stepwise linear VS gradient media. For soft marine sediments, simulations confirm that a large number of modes can be generated in gradient media. Based on pre-processing and theoretical considerations, we extract surface wave dispersion curves from 1-bit CCFs spanning over 400 channels (i.e. ∼2 km) along the array and invert them to image the subsurface. The 2-D velocity profile generally exhibits slow shear wave velocities near the ocean floor that gradually increase with depth. Lateral variations are also observed. Flat bathymetry regions, where sediments tend to accumulate, reveal a larger number of Scholte-wave modes and lower shallow velocity layers than regions with steeper bathymetry. We also compare and discuss the velocity model with that from a previous study and finally discuss the combined effect of bathymetry and shallow VS layers on earthquake wavefields. Our results provide new constraints on the shallow submarine structure in the area and further demonstrate the potential of OBDAS for high-resolution offshore geophysical prospecting.

The role of incoming flow on crystallization of undercooled liquids with a two-phase layer

Motivated by important applications of crystallization phenomena, we consider a directional solidification process for a binary melt with a two-phase (mushy) layer in the presence of weak melt flow. We consider the steady-state solidification scenario, so that the two-phase layer filled with solid and liquid material keeps its thickness. In addition, we consider that the melt flows onto the two-phase layer slowly in the opposite direction to directional crystallization and solidifies there. A complete analytical solution to non-linear two-phase layer equations is constructed in a parametric form, where the solid phase fraction represents a decision variable. The temperature and solute concentration distributions, mushy layer permeability and average interdendritic spacing as well as solidification velocity and mushy layer thickness are analytically determined. We show that incoming melt flow plays a decisive role on mushy layer parameters and internal structures. The solid phase fraction within the two-phase layer and its thickness essentially grow while the mushy layer permeability and average interdendritic spacing decrease with increasing intensity of incoming melt flow.

3D-ambient noise surface wave tomography of Fogo volcano, Cape Verde

Fogo volcano belongs to the Cape Verde Archipelago, and it is one of the most active volcanoes in the Atlantic Ocean, which most recent eruption occurred from November 2014 to February 2015. We analyzed ambient seismic noise recordings of three different networks deployed in the island, totalizing 14 seismic stations, to derive a crustal 3D shear-wave crustal velocity model of the volcano. Through the phase cross-correlation technique followed by a time-domain phase weighted stack, we were able to measure Rayleigh wave group-velocity dispersion measurements in the period range from 1.0 to 10 s. These dispersion measurements were used to invert for 2D group velocity maps at selected periods, and then inverted to produce a 3D shear-wave velocity model of the island. The tomographic model shows three velocity domains. First, an asymmetric upper layer, above 5–6 km of depth, with lower velocities concentrated in the northeastern sector of the island and a clear higher-velocity horizontal body at 3–4 km of depth in the southwestern sector of the island; the spatial correlation between these two velocity zones and the Galinheiros normal fault suggests a genetic link between the high velocities and long-term surface deformation, which we related to sill intrusions between 3 and 4.5 km depth, beneath the southwestern sector of the island. Second, a marked higher-velocity horizontal layer in between 5 and 6 km and 8–9 km, interpreted as the seismic expression of pervasive sill and laccolith intrusions, now cooled, beneath the volcanic edifice and within the underlying oceanic crust. Third, a lower velocity layer below 8–9 km of depth, more pronounced beneath the northeastern sector, which could be explained by a hotter and possibly melt-rich zone beneath the volcano or a significantly altered/serpentinized crust. Finally, our study also confirms that Fogo lacks any sizable magma chambers (ancient or recent) within the volcanic edifice, in agreement with other geophysical and petrological studies. These observations demonstrate that 3D-ambient noise Rayleigh wave tomography is a powerful tool to image the crustal and upper mantle structure beneath volcanic islands, as shown here for Fogo volcano.

Crustal structure of the northern Manila subduction zone: Is thinned continental crust or oceanic crust subducting beneath the Luzon arc and forearc?

Forward and inverse P-wave velocity models along an E-W 280-km-long wide-angle reflection/refraction profile at 21°N across the northeastern South China Sea margin and Manila subduction zone reveal a 10–12 km thick thinned continental crust (TCC) located west of the Manila transcurrent fault (MTF) and Manila slab. The TCC is divided in two parts separated by the intra-continental velocity difference boundary (VDB). West of the VDB, the TCC is located above a high velocity layer (HVL). East of the VDB, the TCC consists of three layers: an undefined body with a velocity inversion at its base above the upper and lower crusts. The VDB and MTF merge east of the Hengchun peninsula showing that the TCC located east of the VDB decreases in size and disappears to the north. The distribution of earthquakes (EQs) shows that ∼80 km of crust have subducted east of the MTF since the onset of Luzon arc collision with Eurasia at ∼7 Ma. All published tomographies suggest the subduction of oceanic crust (OC). However, due to crustal corrections, up to a maximum width of 40 km of TCC might eventually exist in the upper part of the Manila slab instead of OC. Two end-members with 40 km of TCC or not in the upper part of the Manila slab were restored at ∼7 Ma. Since that time, the north Luzon island moved ∼600 km in the northwest while part of this motion was absorbed near the Hengchun peninsula by shrinking of Eurasia TCC, resulting in a ∼ 20° clockwise rotation of the Manila slab and MTF. Small Luzon arc blocks started to rotate 10°-30° clockwise at ∼7 Ma below northern Taiwan, 3–4 Ma in the Coastal range and 1 Ma in Lutao and Lanyu islands and not south of the Hengchun peninsula. Thus, both the clockwise rotation of the individual Luzon arc blocks and of the Manila slab and MTF might explain the collision process of the Luzon arc with the Eurasia continent.

Hierarchical trajectory tracking control for ROVs subject to disturbances and parametric uncertainties

Trajectory tracking control is crucial for a remotely operated underwater vehicle (ROV), but the performance can be degraded due to disturbances, process noises, and parametric uncertainties. Therefore, a hierarchical control scheme is proposed to handle this problem. Firstly, a 4DOF kinematic model and dynamic model of the ROV are constructed. Ocean current disturbance is considered in the kinematic model and the dynamic model when tracking the reference trajectory. Parametric uncertainties are also considered on the dynamic model. Secondly, model predictive control using extended state based Kalman filter (ESKF-MPC) is used to design a kinematic controller (velocity layer) based on the kinematic model to generate virtual expected velocities. ESKF-MPC can not only solve constraints on velocities, but also estimate states and ocean current disturbance, which is beneficial for improving the robustness to ocean current disturbance. Thirdly, adaptive sliding mode control (ASMC) is applied to construct a dynamic controller (position layer) to compute optimal forces and moments based on the dynamic model and virtual expected velocities output by the kinematic controller, which is robust to parametric uncertainties and can solve the chattering problem. Finally, simulations are performed to validate the performance of the proposed hierarchical control scheme.

Empirical H/V spectral ratios at the InSight landing site and implications for the martian subsurface structure

SUMMARY The horizontal-to-vertical (H/V) spectral ratio inversion is a traditional technique for deriving the local subsurface structure on Earth. We calculated the H/V from the ambient vibrations at different wind levels at the InSight landing site, on Mars, and also computed the H/V from the S-wave coda of the martian seismic events (marsquakes). Different H/V curves were obtained for different wind periods and from the marsquakes. From the ambient vibrations, the recordings during low-wind periods are close to the instrument self-noise level. During high-wind periods, the seismic recordings are highly contaminated by the interaction of the lander with the wind and the martian ground. Therefore, these recordings are less favourable for traditional H/V analysis. Instead, the recordings of the S-wave coda of marsquakes were preferred to derive the characteristic H/V curve of this site between 0.4 and 10 Hz. The final H/V curve presents a characteristic trough at 2.4 Hz and a strong peak at 8 Hz. Using a full diffuse wavefield approach as the forward computation and the Neighbourhood Algorithm as the sampling technique, we invert for the 1-D shear wave velocity structure at the InSight landing site. Based on our inversion results, we propose a strong site effect at the InSight site to be due to the presence of a shallow high-velocity layer (SHVL) over low-velocity units. The SHVL is likely placed below a layer of coarse blocky ejecta and can be associated with Early Amazonian basaltic lava flows. The units below the SHVL have lower velocities, possibly related to a Late Hesperian or Early Amazonian epoch with a different magmatic regime and/or a greater impact rate and more extensive weathering. An extremely weak buried low velocity layer (bLVL) between these lava flows explains the data around the 2.4 Hz trough, whereas a more competent bLVL would not generate this latter feature. These subsurface models are in good agreement with results from hammering experiment and compliance measurements at the InSight landing site. Finally, this site effect is revealed only by seismic events data and explains the larger horizontal than vertical ground motion recorded for certain type of marsquakes.

Acoustic viscous boundary layer beyond laminar regime: Particle Image Velocimetry measurements

The current study reports an experimental investigation of flow regimes for acoustically oscillating flows in the near-wall region of a resonator. Particle Image Velocimetry (PIV) is used to measure axial and transverse velocity components inside an empty square resonator over the acoustic cycle for a wide range of Reynolds numbers and at a high Womersley number. The measurements are compared with LDV measurements in a circular duct. A good agreement between the PIV and LDV measurements is observed. The measured transverse distribution of the axial velocity agrees well with the Stokes boundary layer expectations up to the Reynolds number (based on acoustic velocity and viscous boundary layer depth) of 240. At higher Reynolds numbers, the measured velocity distribution deviates from the theoretical expectations, suggesting a change of regime at a Reynolds number between 240 and 272. To assert the critical Reynolds number, the velocity fluctuations and Reynolds stress are estimated. At Reynolds number of 272, an increase in the value of the Reynolds stress is observed at the edge of the viscous penetration depth which is regarded as an indication of changing the flow regime. To better qualify the high amplitude acoustic flow, the spectrum of the turbulent kinetic energy and evolution of the integral length scale over the acoustic cycle are investigated. The decay of turbulent kinetic energy with the wavenumber complies with the universal slope (−5/3). The integral length scale increases during the deceleration stage and decreases at the beginning of the acceleration stage.

Velocity‐layer Zhang equivalency for time‐varying joint limits avoidance of redundant robot manipulator

In the engineering field, a complex system or problem can be transformed into a relatively simple system or problem through equivalency. In this paper, the repetitive motion planning scheme of redundant robot manipulators with time-varying physical limits are to be optimized via Zhang equivalency (ZE) approach, which includes Zhang equality equivalency (ZEE) approach and Zhang inequality equivalency (ZIE) approach. The ZE approach is presented, theoretically proved, and applied to optimize the control scheme of redundant robot manipulators at the velocity layer. After that, an enhanced repetitive motion planning scheme via ZE (ERMPS-ZE) on the basis of quadratic programming is finally built up, which is subject to a ZEE constraint and a time-varying unified ZIE constraint for the solution of RMP in redundant robot manipulator systems. The simulation results on UR10 robot manipulator substantiate superiorities of the proposed scheme with regard to practicality, validity, and completeness over the traditional scheme. In addition, the results of simulation experiments under different limit situations show the adjusting manners and characteristics of the redundant robot manipulator adopting ERMPS-ZE when the manipulator encounters physical limits, which validate the correctness and efficacy of the ERMPS-ZE. Finally, the physical experiment also substantiates the practicability of the ERMPS-ZE.

Three-dimensional multiparticle finite element simulation of dynamic compaction of copper powder by laser shock

A three-dimensional multiparticle finite element method(3D MPFEM) model of laser shock compaction powder was established, and the forming process and densification mechanism of dynamic compaction were studied. The effects of the laser peak pressure(1–5 GPa) on the powder density was studied. The compaction density increased with the laser peak pressure and reached the highest at 5 GPa. A comparison of the different energies of the system revealed that the increase in powder temperature was mainly due to the plastic deformation. In the process of powder springback, large pressure can induce rebound, and the powder may produce an interparticle separation phenomenon due to the difference in particle velocities in different layers. Analysis of the densification process of the inner particles, revealed that the upper layer particles undergo first plastic deformation, and then the second plastic deformation occurs due to the inertia effect, which contributes to the improvement of the powder density. • 3D MPFEM was used to simulate the laser shock powder dynamic compaction process. • Adiabatic temperature rise effect is related to powder plastic deformation. • Laser shock powder has springback phenomenon and large strain rate.

Joint Target and Ionosphere Parameter Estimation in Over-the-Horizon Radar

Target localization, especially the estimation of target altitude, is a challenging task in over-the-horizon radar (OTHR) because of the narrow signal bandwidth as well as the complexity and uncertainty involved in the ionosphere conditions. This task becomes further complicated when the height of the ionosphere layer varies over time. Therefore, it is important to jointly estimate the instantaneous height of the ionosphere and the target altitude as well as other motion parameters. In this article, we achieve these objectives by analyzing the Doppler frequencies of the target local-multipath signals and the clutter. We reveal that the change of the ionosphere height can either enhance or deteriorate the performance of target parameter estimation depending on its direction of motion relative to the target’s motion profile. In addition, it is found that the received target and clutter Doppler signatures follow the chirp signal profile at the OTHR receiver. Based on these observations, we develop a general framework that achieves joint target and ionosphere parameter estimation and accounts for the velocity and accelerations of both target and ionosphere layer. Unlike existing time-frequency-based strategies for target localization and tracking in OTHR, where the Doppler signatures only directly determine target vertical velocity and the target altitude is estimated indirectly, the proposed model enables direct estimation of target altitude and ionosphere parameters. The parameter estimation problem in the proposed strategy is analytically derived and the effectiveness is verified using extensive simulation results.

Ambient Noise Tomography of Jinan: The Migration of Groundwater and the Formation of Geothermal Water

AbstractJinan is an important city in eastern China, with rich groundwater in the region. There are four famous springs in the urban area and an abundance of geothermal water in the northern part, which makes the migration of groundwater in this area a very important issue. To study the shallow shear wave velocity structure and groundwater migration in Jinan, we utilized almost a month of continuous waveform data from 175 short period seismometers deployed by the Chinese Academy of Geological Sciences, in order to calculate the cross‐correlation function. We picked 7749 group dispersion curves and 6117 phase dispersion curves with a period range of 0.2–2 s. Through inversion, we obtained the fine three‐dimensional shear wave velocity and azimuthal anisotropy structure (0–2.4 km). Combining the results with local geological and hydrological data, the following conclusions were reached. (1) There are widespread high velocity anomalies in the region between the Qianfoshan and Wenhuaqiao faults, as well as to the east of the Wenhuaqiao Fault, which may be related to the intrusive gabbro known as the Jinan Intrusive Rock. (2) The two distinct high velocity anomalies in our model (referred to as west and east Jinan Intrusive Rock in this paper) may indicate that the Jinan Intrusive Rock was broken through crustal movement. (3) There is an obvious low velocity layer under the intrusive rock, which could be the channel of groundwater migration. The precipitation in the southern mountain region seeps down into the ground, then is blocked by the Jinan Intrusive Rock and can only progress downwards to a deeper part, where the groundwater is heated by the geothermal gradient. The heated water finally arrives at the northern part and forms geothermal water. (4) The depth of the low velocity layer beneath the Jinan Intrusive Rock varies laterally, which may indicate that the depth of the groundwater migration is different beneath the west and east Jinan Intrusive Rock. (5) There is strong azimuthal anisotropy in southern Jinan, with nearly E‐W fast orientation, which may be related to the tilt limestone layering structure.

Evidence of ground ice melting detected by InSAR and in situ monitoring over permafrost terrain on the Qinghai‐Xizang (Tibet) Plateau

AbstractThe thawing of ice‐rich permafrost has attracted considerable attention in recent years. In this study, we analyzed both the ground surface deformation time series spanning 6 years, derived through the SBAS‐InSAR technique on the Qinghai‐Xizang (Tibet) Plateau (QTP), and the long‐term active layer soil temperature and moisture in situ observations and their relationships. The results showed that long‐term subsidence velocity directly represents the melting of ground ice instead of the thickening rate of the active layer by a quantitative analysis of both terrain subsidence velocity and active layer thickening rate and the increase in liquid water at the bottom of the active layer. Ice‐poor permafrost thawing does not result in distinct subsidence, although the active layer deepening rate can be very high. The spatial analysis reveals that long‐term deformation velocities are large in the foothills and on gentle slopes (1–5 degrees) and are closely related to geomorphological conditions, which could regulate the soil properties and ground ice content. These findings improve the understanding of the thawing degradation of icy permafrost and promote method developments for the automated mapping of ground ice melting in permafrost environments.

A turbulent air‐flow corrugating photovoltaic model to enhance power output

AbstractThis paper investigated the influence of the cooling of turbulent blowing air on the photovoltaic (PV) modules using the corrugation technique. The well‐known five‐parameter diode equation side by side with conservation principles were used to study the effect of corrugating lower PV sides to cool PV's and enhance efficiency. As the main restriction of PV systems is low efficiency that is powerfully counting on its operational temperature, therefore, reducing the operating temperature of PV cells is critical for the PV panel to work. To achieve this aim, a mathematical model describing PV temperatures and efficiency using continuity, momentum, and energy side by side with the Shockley diode equation was built. It was found that the corrugating of lower sides of PV's up to 1 mm in a distance of 20 mm considering turbulent flow conditions considerably reduced temperature and consequently enhanced thermal efficiency from 13% to 15%; the eddy viscosity and Reynolds shear stress increased boundary layer thickness and velocities, so increased the coefficient of heat transfer and consequently electrical power output and thermal efficiency.