Non-uniform Velocity Research Articles

A novel wall interference correction method for airfoil

Corrections for wind tunnel experimental results are crucial when accounting for tunnel wall interference. This study introduces a new method, the non-uniform wall pressure signature method (NUWPSM), which is designed to address tunnel wall interference in airfoil. The improved wall pressure signature method (WPSM), an enhanced version of the WPSM, is developed to address the velocity disparities and systematic errors in pressure measurements between with and without model conditions. Furthermore, the NUWPSM considers the non-uniformity of the flow induced by the limited far-field effect in wind tunnel experiments. Utilizing experimental data from three different scaled models of the WA210 airfoil, the efficacy of both the Improved WPSM and NUWPSM is verified. Results indicate that the Improved WPSM exhibits superior capabilities in simulating the distribution of axial induced velocity along the wall compared to the traditional WPSM. Additionally, both the Improved WPSM and NUWPSM demonstrate comparable abilities in correcting tunnel wall interference, achieving precise corrections within an angle of attack range of −180° to +180°. Notably, the NUWPSM effectively captures the velocity non-uniformity induced by the limited far-field effect, thereby extending its applicability to a broader range of scenarios. Furthermore, the NUWPSM showcases enhanced robustness by eliminating human intervention in the singularity quantity and distribution.

Experimental and numerical research on a C-type heat exchanger in duct air conditioner under non-uniform airflow

The indoor unit of duct air conditioner typically employs an A-type heat exchanger (HX), but non-uniform airflow within the duct significantly degrades heat transfer performance. The current study proposes a C-type HX to accommodate the non-uniform airflow better. Experiments are conducted to compare the C-type and A-type HXs under varying conditions, including air volume flow rate, air velocity non-uniformity, inlet air temperature, and condensing temperature. Results indicate that as the non-uniformity of inlet air velocity increases, the heat transfer capacity of A-type HX decreases obviously. In contrast, the C-type is insensitive to the non-uniform air velocity distribution, which consistently outperforms the A-type in terms of heat transfer capacity throughout various operating conditions. Additionally, a numerical model is developed to compare the local parameters of the two HX types. The C-type demonstrates a more uniform outlet air temperature and exhibits a heat transfer capacity that is 19.1% higher than the A-type, while maintaining the identical heat transfer area and size parameters.

Swirling instability of viscous liquid jets with axial shear effect in gas surroundings

Linear instability analysis of a viscous swirling liquid jet surrounded by ambient gas is carried out by considering the significant influence of axial shear effect. The jet azimuthal flow is assumed as a Rankine vortex, and the non-uniform velocity distribution in the jet axial direction is approximated by parabolic and error functions. The enhancement of jet rotation is found to promote the predominant mode with larger azimuthal wavenumbers, and the mode transition is decided by the competition between centrifugal force and axial shear stress. Subsequently, the influence of the axial shear effect is examined through changing the degree of shear stress and the thickness of the gas velocity boundary layer. It is found that an increase of jet average velocity or surface velocity in the axial direction leads to the predominant mode transition to smaller azimuthal wavenumbers, due to the combined effects of shear stress and gas pressure perturbation. A larger velocity difference between ambient gas and liquid jet also promotes the predominant modes with smaller azimuthal wavenumbers, and the physical mechanism is attributed to gas pressure perturbation. Phase diagrams of different azimuthal modes are given and compared with the study of Kubitschek & Weidman (J. Fluid Mech., vol. 572, 2007, pp. 261–286), where a static swirling column without axial shear stress was considered. The strengthened axial shear effect is found to delay the transition of predominant modes with the increase of angular velocity. Experimental studies considering the swirling jets with different axial velocities are further carried out, which validate the theoretical findings. Different instability mechanisms and their transition rules are also identified through energy budget analysis. This study is expected to give scientific guidance on understanding the instability mechanisms of the swirling jets that widely exist in natural phenomena and engineering applications.

Numerical simulation of radial duel-stage nozzle vortex cooling at the leading edge of a gas turbine blade

Thermal failure is one of the major challenges faced by the leading edge of gas turbines, which significantly affects the improvement of their efficiency. The vortex cooling technique has become a promising solution to address this issue. Radial duel-stage nozzle vortex cooling (RDNVC) model, featured with a vortex tube and two sets of nozzles, is proposed based on the radial single-stage nozzle vortex cooling (RSNVC) configuration. This novel structure aims to intensify turbulence within the cooling fluid at the nozzle inlets, thereby improving heat transfer at the leading edge. The model improves turbulence in the cooling fluid, promoting better heat transfer at the leading edge. Numerical simulations with the SST k-ω turbulence model were performed to analyze heat transfer and flow characteristics at varying Reynolds numbers (Re). The results show that the non-uniform inlet velocity in RDNVC increases turbulence and vorticity inside the vortex tube, leading to improved heat transfer. At the same cooling airflow rate, RDNVC increased the global average Nusselt number by 23.56% compared to RSNVC. Nu increases with Re. Among the three models, RDNVC(6–2) (nozzle heights of 6 mm and 2 mm) showed the best thermal performance, followed by RDNVC(2–6), while RSNVC had the lowest thermal performance. For the same pressure drop, RDNVC(2–6) achieved an 8.42% improvement in heat transfer efficiency over RSNVC. Based on Re and geometry parameters, the empirical correlation for the global average Nusselt number of RDNVC is also proposed.

Double-diffusive convection in flow of Carreau fluid with variable density inside converging and diverging channels of rectilinear walls

In this article, the effects of double-diffusive convection have been seen on the flow of Carreau fluid of variable density, maintained inside straight and converging (diverging) channels. Note that the channel walls exhibit variable porosity and undergo stretching or shrinking at non-uniform velocities. In the flow domain, we have taken into account the convective transport of both heat and species mass concentrations. The pseudo-similarity solutions of previous investigation for such type flows are not used here; however, a new set of similarity transformations has been formed, which reduced the governing system (PDEs) into an exact set of ordinary differential equations (ODEs), whereas the longstanding issues of semi-similarity solutions have been successfully resolved in this particular case and in general for all situations of Carreau fluid flow. In a nutshell, a unified mathematical approach has been devised in this paper. We strictly emphasized the simulation of flow of Carreau fluid and double diffusive convection in flow inside a channel with multiple dynamical behaviours and structures (both Jeffery Hammel and Poissuielle flow types) of walls. The boundary layer approximation and stream function assumptions have not been used in the study's execution. The shear thinning and shear thickening features of Carreau fluids with variable density cause them to exhibit lower axial velocity in the centre of a horizontal channel than Newtonian fluids due to variable wall configurations and complex flow conditions. By enhancing buoyancy driven convection, which promotes effective heat dispersion, increasing the solutal and thermal Grashof numbers (GrS=GrT>0) lowers the temperature field. It has been found that in channel with diverging walls (a1=2.0), increasing the modified Reynolds numbers (σ1,σ2>0) increases concentration profiles, i.e. ϕ(η), while decreasing them in channel with rectilinear walls (a1=0.0).

Investigation on the hydraulic loss in the vertical inlet and outlet of a pumped storage power station

Abstract The vertical inlet/outlet is commonly adopted in the upper reservoir of pumped-storage power stations, in which the internal flow patterns exert a critical influence on the safety and operational efficiency of the entire power station. Based on the standard k-ε turbulence model coupled with the revised wall roughness theory, this investigation presented a numerical model of a vertical inlet/outlet in a pumped-storage upper reservoir and the validity and accuracy of the numerical simulation are validated through comparison well with the results of the model experiments. The results suggest that the emergence of vortices of varying intensities near the inlet during power-generation scenarios at dead water levels and at 3.5 times of the rated flow rate (389.6 m3/s). The bend section experiences fairly nonuniform flow velocity, with the highest average flow hydraulic loss in the entire vertical pipe inlet/outlet system. These insights provide a substantial utility for operational strategies and optimization designs in related engineering projects.

A quantum algorithm for the lattice-Boltzmann method advection-diffusion equation

We present a versatile and efficient quantum algorithm based on the Lattice Boltzmann method (LBM) approximate solution of the linear advection-diffusion equation (ADE). We emphasize that the LBM approximation modifies the diffusion term of the underlying exact ADE and leads to a modified equation (mADE). Due to its versatility in terms of operator splitting, the proposed quantum LBM algorithm for the mADE provides a building block for future quantum algorithms to solve the linearized Navier-Stokes equation on quantum computers. We split the algorithm into four operations: initialization, collision, streaming, and calculation of the macroscopic quantities. We propose general quantum building blocks for each operator, which adapt intrinsically from the general three-dimensional case to smaller dimensions and apply to arbitrary lattice-velocity sets. Based on (sub-linear) amplitude data encoding, we propose improved initialization and collision operations with reduced complexity and efficient sampling-based simulation. Quantum streaming algorithms are based on previous developments. The proposed quantum algorithm allows for the computation of successive time steps, requiring full state measurement and reinitialization after every time step. It is validated by comparison with a digital implementation and based on analytical solutions in one and two dimensions. Furthermore, we demonstrate the versatility of the quantum algorithm for two cases with non-uniform advection velocities in two and three dimensions. Various velocity sets are considered to further highlight the flexibility of the algorithm. We benchmark our optimized quantum algorithm against previous methods employed in sampling-based quantum simulators. We demonstrate sampling efficiency, with sampling accelerated convergence requiring fewer shots.

Numerical modeling of thermophoresis and Brownian with heat transfer in shear-rate-dependent fluid: The finite element simulations

This article discusses the simultaneous influence of thermophoresis, Brownian motion, and the dispersion of nanoparticles on thermal enhancement in non-Newtonian fluid existing over a surface stretching with non-uniform velocity. The modeled problems describing the transport of heat by the fluid are boundary value problems and are solved by the finite element method (FEM). The mesh-free analysis is done and accuracy is checked. The numerical solutions are computed and used for depicting flow field behaviors. It is visualized that Cu− Prandtl fluid and Cu−Al2O3− Prandtl fluid flow are affected in opposing ways by Prandtl and elastic factors. As a result, momentum in the Newtonian fluid does not penetrate as quickly as that does in Prandtl fluid. The Brownian motion parameter is responsible for a decrease in the Nusselt number whereas the thermophoresis parameter causes a decrease in the Sherwood number. Thus, it is essential to note that the wall heat transfer rate in the fluid can be enhanced by making arrangements to reduce Brownian motion. Similarly, wall mass flux can be controlled through the thermophoresis parameter. Nusselt and Sherwood number has shown an increasing tendency when the Prandtl parameter is increased. Thus, fluids with higher Prandtl fluid parameters are suitable for higher wall heat and mass fluxes. The temperature of mono and hybrid nano-Prandtl fluids is increased by caused by thermophoresis and Brownian motion.

Study on heat transfer performance of cooling channels in proton exchange membrane fuel cells based on topology optimization

Based on topology optimization method, a dual-objective function topology optimization model containing minimum average temperature and minimum flow power dissipation was established in this study. Coupled with the uneven heat generation model of proton exchange membrane fuel cells, the optimal layout scheme under the target operating conditions was adaptively obtained. The effects of volume fraction, objective function weight, and parabolic inlet velocity on the flow channel structure and cooling performance of topological cooling plates were studied. The results indicate that with the increase of volume fraction, the area of fluid region increases, the average temperature and the pressure drop of cooling plate gradually decrease. At the volume fraction of 0.5, the cooling plate has the best cooling performance. The temperature difference and maximum temperature reach the minimum values of 5.45 K and 347.58 K, respectively. When the volume fraction increases from 0.4 to 0.6, the pressure difference decreases by 67.64 %. With the increase of temperature weight coefficient, the area of high-temperature area gradually decreases, and the temperature uniformity is significantly improved. When the inlet velocity of coolant is 0.025 m/s and the temperature weight coefficient is 0.9, the average and maximum temperatures of cooling plate reach the lowest values, which are 343.53 K and 344.51 K, respectively. The maximum temperature of cooling plate under parabolic inlet velocity is of 347.87 K, which is 0.29 K higher than that under uniform inlet velocity. Non-uniform coolant inlet velocity will lead to a decrease in heat transfer capacity of cooling plate and an increase in coolant power consumption.

Application of the magnetic tracer-tracking system in solids circulation measurement in a fluidized bed standpipe

In the present study, the application of a magnetic tracer-tracking method in measuring solids circulation in a fluidized bed standpipe is investigated, due to its advantages of little intervention and cost efficiency, especially in pressurized systems. The method only needs to inject one small magnetic tracer to follow the main solid flow in the standpipe, therefore predicting particles’ real-time velocities. The measurement accuracy was thoroughly tested via comparing to conventional descending and accumulation methods. Main tracer properties, including tracer shape, density, and magnet core, were considered. Solids flow patterns in the standpipe were also regulated by changing orifice sizes and adding an inclined pipe, for the purpose of investigating the measurement accuracy in various conditions. The adverse effect of a narrow orifice on measurement was addressed via constructing a model that includes sand particles’ non-uniform velocity distribution across the standpipe cross-section. To interpret behaviors of tracers varied in size and density, a mathematical model was constructed to describe forces exerted on the tracer in the solids bed. The behaviors of the tracer immersed into the solids bed were also examined, providing an insight to that in a standpipe with continuous solids circulation. The solids bed density was also regulated by varying the mixture of olivine sand and carbonaceous particles at different proportions. The magnetic tracer-tracking method has been successfully validated, demonstrating good measurement accuracy of solids discharge flow rates in the standpipe, particularly avoiding cumbersome calibration. Moreover, the method can also determine sand waving and oscillated discharge behaviors, which might be related to solids’ stick–slip phenomena and is unlikely to be accurately determined using conventional descending and accumulation methods.

On the Challenges of Integrating a Rotating Detonation Combustor with an Industrial Gas Turbine and Important Design Considerations for Row-1 Blades

Abstract In an effort to increase the efficiency and performance of gas turbine power cycles, pressure gain combustion (PGC) has gained significant interest. Since Rotating Detonation Combustors (RDC) can provide a quasi-steady mode of operation, research has been triggered to integrate RDC with power-generating gas turbines. However, the presence of subsonic and supersonic flow fields which are generated due to the shock waves that stem from the detonation wave front and the highly non-uniform temperature and velocity profiles may cause a depreciation in the turbine performance. The current study seeks to investigate the challenges of integrating the RDC with nozzle guide vanes (NGV) of an industrial, can-annular gas turbine and attempts to understand the major contributors that impact efficiency and identify the key areas of optimization that need to be considered for maximizing performance. The RDC was integrated with the NGVs through a non-optimized straight duct-type geometry with a diffuser cone. 3-Dimensional Numerical analyses were performed to investigate sources of total pressure loss and to understand the unsteady effects of RDC which contribute towards the deterioration of performance. The entropy generation at different regions of interest was calculated to identify the major irreversibilities in the system. Also, total pressure and temperature distribution along the radial direction at the exit of the transitional duct is presented.

Thermal recycling analysis in regenerative cooling channels based on liquid rocket engine cycles

For rocket cycles involving electric pumps, gas generators, expanders, and staged combustion, a thermal recycling method is proposed to provide a more realistic simulation of regenerative cooling systems in liquid rocket engines. This method simulates a real situation where the outlet of the cooling channel is thermally recycled through the turbine or preburner to the inlet of the combustion chamber. Supercritical fluid properties are determined using the extended Redlich–Kwong (RK)–Peng–Robinson (PR) real-fluid equation of state. The axisymmetric reacting flows of a thrust chamber with regenerative cooling channels are simulated using the flamelet-based lookup table. To account for the multi-injector effect in the two-dimensional axisymmetric simulation, a non-uniform velocity distribution is implemented, utilizing exponential distributions of each injector’s mass flow rate. For the hot gas temperature, coolant temperature, and cooling mass flowrate, the thermal recycling method is comparatively analyzed with the thermal decoupling method. The regeneration effect of the heated fuel is explored by evaluating the inflow energy, reaction energy, wall heat transfer, and the exit kinetic energy conversion. The thermal recycling method is developed for regeneratively cooled rocket engines with the expander, gas generator, staged combustion, and electric-pump cycles. Through this numerical procedure, the thermal recycling method is successfully applied to a liquid oxygen/methane engine and NASA’s Crew Exploration Vehicle nozzle with two types of cooling. Based on the results of the four types of rocket cycles, it is confirmed that the specific impulse increases by 1.5–2% due to the regenerative heat effect.

Environmental hazard assessment of forest fire sites to firefighting aircraft—part I: Canyon wind and temperature distribution

Wildfires have caused immense damage to the environment, property and human safety in recent years. Fortunately, the deployment of firefighting aircraft, particularly water bombers, has emerged as one of the most effective strategies for combating wildfires. However, the intricate environment of forest fire sites, characterized by thermal turbulence and canyon winds, presents a formidable flight risk for firefighting aircraft. To address this issue, this study conducted a comprehensive risk assessment of firefighting aircraft operating in a wildfire environment, analyzing the impact of thermal turbulence and canyon winds using a finite element simulation method. This approach not only bridges the research gap in the field of flight safety but also evaluates the environmental risks encountered by firefighting aircraft when entering forest fire sites. Our findings underscore thermal turbulence and canyon winds as potential hazards for aircraft flying over mountainous terrain, elucidating the effect of thermal turbulence on aircraft engine intakes and quantifying the total lift loss incurred during encounters with canyon winds featuring non-uniform airflow velocities. Specifically, thermal turbulence can induce instability and vibration in aircraft engines, whereas canyon winds can generate updrafts and downdrafts that may compromise aircraft structures or lead to lift loss. Furthermore, we cite several references to emphasize the multifaceted risks associated with the forest fire site environment, encompassing temperature gradients, thunderstorms, and air pollution. Such comprehensive wildfire data can be invaluable in assessing the flight safety of firefighting aircraft during water-dropping missions in forest fire scenarios.

Evolution of pore-scale concentration PDFs and estimation of transverse dispersion from numerical porous media column experiments

Knowing local concentration distributions is important for transport and mixing, particularly in porous media, yet a comprehensive understanding of them remains a challenge. Computing advancements have enabled high-resolution pore-scale simulations, offering an unprecedented opportunity for in-depth investigation of mixing. In this study we use simulation data to examine concentration distributions at the pore scale in the context of longitudinal (pseudo-one-dimensional) solute transport through a porous column. These distributions arise in a single column from heterogeneous flow at the pore-scale, which gets averaged out when upscaled and are not with reference to statistics across multiple random realizations. To measure these distributions, we first devise a semi-analytical approach to estimate the mean effective transport velocity profile for a non-uniform Darcy-scale fluid velocity, which unavoidably occurs due to the presence of lateral boundaries. This development allows sampling micro-scale concentrations over a moving surface that possesses a well defined Darcy-scale mean concentration, enabling empirical computation of the local concentration distribution. As an added benefit we find that our approach allows for the estimation of transverse dispersion coefficients, which is not typical in traditional column experiments. The implemented approach can estimate it via inverse modeling, and it agrees closely with previously published experimental data across the range of Peclet numbers we studied. We found that the measured pore-scale concentration probability density functions are best represented by a beta distribution, thus validating this longstanding hypothesis with direct evidence. Furthermore, we propose a model to describe the temporal and spatial evolution of the local concentration pdf, as well as its Péclet number dependence.

An upscaling model for simulation of geothermal processes in stratified formations

In stratified porous media, non-uniform velocity between layers combined with thermal conduction across layers causes spreading of the thermal front: thermal Taylor dispersion. Conventional upscaling not accounting for this heterogeneity within simulation grid blocks underestimates thermal dispersion, leading to overestimation of thermal breakthrough time. We derive a model for effective longitudinal thermal diffusivity in the direction of flow, αeff, to represent the effective thermal dispersion in two-layer media. αeff, accounting for thermal Taylor dispersion, is much greater than the thermal diffusivity of the rock itself. We define a dimensionless number, NTC, a ratio of times for longitudinal convection to transverse conduction, as an indicator of transverse thermal equilibration of the system during cold- or hot-water injection. For NTC > 5, thermal dispersion in the two-layer system closely approximates a single layer with αeff. This suggests a two-layer medium satisfying NTC > 5 can be combined into a single layer with an effective longitudinal thermal diffusivity αeff. In application to a geothermal reservoir, one can apply the model to perform upscaling in stages, i.e. combining two layers satisfying the NTC criterion in each stage. The αeff model accounting for the fine-scale heterogeneity within simulation grid blocks would enhance the prediction accuracy of thermal breakthrough time and thus thermal lifetime.

Skyrmion motion induced by spin-waves on magnetic nanotubes

Abstract We investigate the skyrmion motion driven by spin waves on magnetic nanotubes through micromagnetic simulations. Our key results include demonstrating the stability and enhanced mobility of skyrmions on the edgeless nanotube geometry, which prevents destruction at boundaries — a common issue in planar geometries. We explore the influence of the damping coefficient, amplitude, and frequency of microwaves on skyrmion dynamics, revealing a non-uniform velocity profile characterized by acceleration and deceleration phases. Our results show that the skyrmion Hall effect is significantly modulated on nanotubes compared to planar models, with specific dependencies on the spin-wave parameters. These findings provide insights into skyrmion manipulation for spintronic applications, highlighting the potential for high-speed and efficient information transport in magnonic devices.

Analysis of the velocity non-uniformity in waterjet inlet duct

Abstract Since the waterjet propulsion unique advantages, it’s applied more widely. But the Inlet duct and other structures prone to particular flows. Since the inlet duct of a special structure, the velocity distribution shows non-uniformity, departing from the waterjet pump design scenarios. In this paper, waterjet pump is simulated to study its velocity non-uniform of inlet duct and to investigate the discipline of the velocity distribution. By changing the inlet boundary conditions, the corresponding velocity field is obtained, to analyze the results under different conditions. It is researched the effect of inlet duct velocity non-uniformity on waterjet propulsion system.

On the resonance frequency of the irregular shaped visco-acoustic Helmholtz cavity problem

In this paper we develop a closed-form mathematical solution for the resonance frequency of the axisymmetric irregular shaped visco-acoustic Helmholtz cavity problem. The solution is based on a conformal mapping that transforms the governing visco-acoustic equations of motion for the irregular cavity geometry into a new domain described by a set of orthogonal curvilinear coordinates. These orthogonal curvilinear coordinates have an important characteristic relative to the transformation of the physical boundary: the mapped domain is constructed such that the locus of all points for the length-wise profile of the physical boundary coincides with a constant value for a (quasi radial) coordinate in the new mapped domain. In these orthogonal curvilinear coordinates we obtain an analytical solution for the visco-acoustic equations of motion and exactly satisfy the no-slip fluid boundary conditions over the irregular shaped cavity walls by matching the coefficients of an orthogonal Legendre polynomial series representation for the non-uniform velocity on the cavity walls. The mathematical solution is an approximation to the extent that the scale factors chosen for the mapping consist of strictly the mutual-coupling terms of the true scale factors. Thus we analyze some results to understand the correlation of the analytical solution frequency response spectra with numerical finite element analyses of the idealized boundary conditions with various irregular shaped cavity geometries. The results for fundamental resonance frequency were found to exhibit good correlation with the results of finite element analyses over a significant range of fluid properties with different irregular cavity geometries. As the primary motivation for the derivation stems from the lack of a rapid yet accurate alternative to computationally intensive MultiPhysics FEA in the formulation of acoustic trendlines for sensor development, the solution’s acoustic impedance was applied as dispersive loading in a simple lumped parameter model of a fluid identification sensor for comparison. The resulting acoustic trendlines of the reduced (5 DOF) model were found to exhibit good correlation with the results of the MultiPhysics FEA (>105 DOF). Thus the solution was found to enable a closed-form analytical method for rapid construction of parametric studies in the practical design of fluid analysis sensors based on complex resonant cavity geometries.

Individual particle approach to diffusive shock acceleration. Effect of the non-uniform flow velocity downstream of the shock

The momentum distribution of particles accelerated at strong non-relativistic shocks may be influenced by the spatial distribution of the flow speed around the shock. This phenomenon becomes evident in the cosmic-ray-modified shock, where the particle spectrum itself determines the profile of the flow velocity upstream. However, the effects of a non-uniform flow speed downstream are unclear. Hydrodynamics indicates that the spatial variation of flow speed over the length scales involved in the acceleration of particles in supernova remnants (SNRs) could be noticeable. In the present paper, we address this question. We initially followed Bell's approach to particle acceleration and then also solved the kinetic equation. We obtained an analytical solution for the momentum distribution of particles accelerated at the cosmic-ray-modified shock with spatially variable flow speed downstream. We parameterised the downstream speed profile to illustrate its effect on two model cases: the test particle and non-linear acceleration. The resulting particle spectrum is generally softer in Sedov SNRs because the distribution of the flow speed reduces the overall shock compression accessible to particles with higher momenta. On the other hand, the flow structure in young SNRs could lead to harder spectra. The diffusive properties of particles play a crucial role as they determine the distance the particles can return from to the shock, and, as a consequence, the flow speed that they encounter downstream. We discuss a possibility that the plasma velocity gradient could be (at least partially) responsible for the evolution of the radio index and for the high-energy break visible in gamma rays from some SNRs. We expect the effects of the gradient of the flow velocity downstream to be prominent in regions of SNRs with higher diffusion coefficients and lower magnetic field, that is, where acceleration of particles is not very efficient.

Shallow crustal imaging beneath NW Indian terrane from teleseismic P-wave coda using a Bayesian approach

Deciphering the crustal architecture of the Cretaceous Barmer-Sanchore Basin (BSB) and Neoproterozoic provinces in the NW Indian Shield presents significant challenges due to extensive sediment deposition and widespread felsic igneous rocks. To address such intricacies, we employ a transdimensional Bayesian joint inversion of teleseismic P-wave polarizations and receiver functions to resolve the detailed structure of the upper 10 km of the crust beneath 29 seismic stations deployed in the study area. The new data is analyzed separately within each of the three different backazimuthal groups to identify any strong variations in the shallow subsurface structure and derive a more robust, averaged model for every station site. The resulting 1-D models reveal heterogeneous sediment cover in BSB and Marwar Basin, with respective thicknesses ranging from ∼1.3–5.5 km and 1–1.5 km. Remarkably low shear-wave velocities (Vs < 1.0 km/s) of sediments with increased Vp/Vs (>2.3) are observed in BSB and adjacent areas, which are related to highly unconsolidated Quaternary-Tertiary deposits. The Marwar Basin is imaged to have 0.3–0.5 km of uncompacted sediments that overlie 0.5–1 km thick Marwar Supergroup sequence. The Erinpura Granites (EG) and Malani Igneous Province (MIP) are characterized by a variably thick sediment blanket, typically ranging within 1 km in thickness. The Vs of the sediments in these regions exceeds 2.4 km/s that possibly corresponds to Mesozoic and older sediments. The basement beneath EG exhibits Vs faster than 3.4 km/s, consistent with moderately metamorphosed granites. In MIP, the basement is characterized by non-uniform shear velocities, suggesting the influence of intrusions linked to magmatic episodes in NW India.