Fluid Velocity Research Articles

Enhanced heat transfer in novel star-shaped enclosure with hybrid nanofluids: A neural network-assisted study

The current research is a numerical investigation of the thermo-fluidic transport trend within a new star-shaped enclosure filled with Fe3O4−MWCNT (Multiwall Carbon Nanotubes) suspended hybrid nanoparticles in a base fluid (water), induced by a horizontal magnetizing field. A rectangular rod inside the cavity positioned at center is kept at a high temperature, as the low temperature is chosen for outer corrugated boundary. Formulation yelled in mathematical principles, along with the boundary conditions and some physical assumptions, are formulated as dimensionless PDEs. The finite element method (FEM) assisted by “COMSOL” software, employed for numerical simulations, and the PARDISO solver is used for solving nonlinear system of equations. Also, an artificial neural network (ANN) model is assembled to analyze the effect of these parameters on thermal and flow transport properties of Hybrid nanofluid. The training of this ANN model is done by a dataset generated from numerical simulations, suggesting predictions regarding heat transport under varying parameters. This approach does not only reduce the effort, but also reduces computing time when exploring the thermal behaviors across various datasets. The visualization of velocity and temperature fields through streamlines and isotherms, along with the evaluation of the Nusselt number, illustrate the enhanced heat transfer facilitated by the incorporation of Fe3O4−MWCNT nanoparticles. The results show that increased magnetic field strength reduces fluid velocity due to the generated Lorentz force, which counteracts convective flow. Percentage analysis indicates that hybrid nanofluids (Fe3O4−MWCNT) significantly improve thermal distribution compared to conventional fluids. This study demonstrates the effectiveness of ANN models in forecasting the influence of diverse factors on the flow and heat transport characteristics of hybrid nanofluids. These insights are essential to the design and optimization of heat transfer systems.

Evaluation of the effects of maintaining a moderate humidity (50–60%) and increased air movement on litter moisture and footpad health in a commercial broiler house

Evaluation of the effects of maintaining a moderate humidity (50–60%) and increased air movement on litter moisture and footpad health in a commercial broiler house

A Comparison of a Three Blade and Five Blade Wind Turbine in Terms of the Mechanical Properties Using the Q-Blade Software

يمكن لتوربينات الرياح المنتشرة في مزارع الرياح على نطاق المرافق أن تدعم تلبية رغبات الطاقة المستقبلية وتقليل انبعاثات ثاني أكسيد الكربون عن طريق تقليل متطلبات الطاقة من الوقود الأحفوري. مع ارتفاع درجة حرارة الهواء على مدار اليوم، تزداد سرعة الرياح بسبب تدرجات درجة الحرارة، والتي تنتج تدرجًا في الكثافة / الضغط، مما يؤدي إلى حركة الهواء التي تواجهها توربينات الرياح. اعتمادًا على تضاريس الأرض، يمكن أن تواجه الرياح وتوجه في الوديان بين التلال وفوقها حيث تتدفق وتتبع منحنيات الأرض. تنتج هذه التضاريس زيادة في سرعة الرياح في القمم والتلال. في هذا العمل، تم تصميم شفرة دوار توربينات الرياح الأفقية الصغيرة للعمل في ظل سرعة الرياح المنخفضة، باستخدام برنامج (Q-Blade). استنادًا إلى نظرية عنصر الشفرة (BEM). مع الجنيح NACA3712. تم استخدام دوار ثلاثي الشفرات ودوار بخمس شفرات بناءً على نوع التوربين وحجم الدوار لتوليد الطاقة الميكانيكية من طاقة الرياح. تم إجراء مقارنة وتحليل قوة التوربين ومعامل القدرة ومعامل عزم الدوران عند سرعة رياح منخفضة ((1m/s-8m/s وتم الحصول على نتائج دقيقة للغاية. وجد أن أفضل أداء يمكن أن يعمل فيه دوار توربيني ثلاثي الشفرات بقدرة توربينية تبلغ (955W) كما تم الحصول على قدرة التوربين ((582W للدوار خماسي الشفرات. وجد أن تصميم توربينة رياح أفقية صغيرة بخمس ريش أفضل من التوربين بثلاث ريش ومناسب للعمل في المناطق ذات سرعة الرياح المنخفضة وبكفاءة عالية مقارنة بحجم التوربين.

Responses of summer mesoscale convective systems to irrigation over the North China Plain based on convection-permitting model simulations

Extensive irrigation activities in the North China Plain (NCP) significantly influence regional weather and climate. However, previous studies focusing on the NCP were primarily based on coarse-resolution models, which are unable to explicitly resolve convection systems, causing large uncertainty in precipitation simulations. In this study, a convection-permitting model coupled with a dynamic irrigation scheme is utilized to investigate the impacts of irrigation on summertime mesoscale convective systems (MCSs) over the NCP. Sensitivity experiments with irrigation off and on are conducted for 5 summers and an MCS identification and tracking algorithm is applied to both satellite observations and model simulations. We find that incorporating irrigation in the model increases MCS precipitation, which agrees more with observations. The probability distributions of MCS lifetime, area, propagation speed, and intensity are all better simulated with irrigation. Irrigation increases the occurrence frequency of MCSs throughout the entire day. The nighttime increase is partly because of more frequent local initiation of MCS developed from isolated deep convection, while the daytime increase is mainly attributed to the changes in MCSs initiating elsewhere and then propagating to the NCP. On average, irrigation induces additional moisture that is more thermodynamically favorable for precipitation, but this effect is partially offset by the weakened ascending air motion primarily caused by irrigation surface cooling. Compared to weak MCS precipitation events, strong MCS precipitation events experience greater enhancement in precipitation intensity when including irrigation because the offset effect from the change in large-scale ascending air motion is insignificant. In addition, irrigation makes the variation of MCS precipitation intensity more correlated with the variation in ascending motion but less correlated with that in atmospheric moisture. Our results suggest the pronounced impacts of irrigation on MCSs over the NCP which should be included in numerical models to improve regional precipitation simulation and prediction.

Self-chemophoresis in the thin diffuse interface approximation

Self-chemophoresis is an appealing and quite successful interpretation of the motility exhibited by certain chemically active colloidal particles suspended in a solution of their ‘fuel’: the particle has a phoretic response to self-generated, rather than externally imposed, inhomogeneities in the chemical composition of the solution. The postulated mechanism of chemophoresis is the interaction of the particle (via an adsorption potential) with the chemical inhomogeneities in the surrounding medium. When the range of this interaction is much smaller than any other relevant scale in the system, the (translational and rotational) phoretic velocities can be described in terms of a phoretic coefficient and a slip fluid velocity at the surface of the particle. Using the case of a spherical particle as a simple and physically insightful example, here we exploit an integral representation of the rigid-body motion to critically re-examine this framework. The systematic analysis highlights two steps in the approximation: first the thin–layer approximation (very large particle size), and subsequently a lubrication approximation (slow variation of the adsorption potential along the tangential direction). We also discuss how these approximations could be relaxed and the effect of this on the particle's motion.

Effect of chemical reaction on MHD Casson natural convection flow over an oscillating plate in porous media using Caputo fractional derivative

Fractional calculus is a branch of mathematics that extends the traditional definitions of calculus to include non-integer exponents. It has been successfully used to model a variety of physical processes, including the coiling of polymers, viscoelasticity, traffic flow, diffusive transport, fluid dynamics, electromagnetic theory, and electrical networks. However, fractional calculus has not yet been widely used to study the physical properties of non-Newtonian fluids flowing over accelerating porous plates. The present research examines the unsteady Casson flow over an infinitely horizontal porous plate, MHD and porosity impacts on fluid velocity are also discussed. The major goal here is to develop analytical outcomes for the tran-sient incompressible MHD Casson flow over an accelerating porous plate. This plate is oscillating in the x-direction and infinitely large in the y-direction and fluids flowing over it at y > 0 due to oscillation. Choosing the right choice of dimensionless variables allows the model's governing equations to become dimensionless. These dimensionless differential equations of the Casson fluid are calculated by applying the Laplace transform method. On velocity, the impacts of different factors are investigated. They are time, porosity parameter, oscillation frequency of plate, magnetic parameter, and Casson fluid parameter. As we rise the Casson flow parameter values, magnetic parameter, and Prandtl number we observe that the velocity drops. In contrast to other factors, the effects of Grashof number, oscillation frequency, fractional parameter, and porosity on the velocity profile are reversed. Using Mathcad software, graphs are sketched for various values of these parameters and are thoroughly described. The fluid properties discovered signif-icant findings and disclosed several characteristics for a range of flow parameters and fractional parameter values. Increasing the values of fractional parameters is shown to improve the characteristics of fluids, and this is beneficial in fitting experimental data related to heating and cooling processes, particularly in electronic equipment.

Mesoscale air motion and thermodynamics predict heavy hourly U.S. precipitation

Predicting heavy precipitation remains scientifically challenging. Here we combine Atmospheric Infrared Sounder (AIRS) temperature and moisture soundings and weather forecast winds to predict the formation of thermodynamic conditions favourable for convection in the hours following satellite overpasses. Here we treat AIRS retrievals as air parcels that are moved adiabatically to generate time-varying fields. Over much of the Central-Eastern Continental U.S. during the non-winter months of 2019–2020, our derived convective available potential energy alone predicts intense precipitation. For hourly precipitation above the all-hours 99.9th percentile, performance is marginally lower than forecasts from a convection permitting model, but similar to the ERA5 reanalysis and substantially better than using the original AIRS soundings. Our results illustrate how mesoscale advection is a major contributor to developing heavy precipitation in the region. Enhancing the full AIRS record as described here would provide an alternative approach to quantify multi-decade trends in heavy precipitation risk.

Blade redesign based on inverse design method for energy performance improvement and hydro-induced vibration suppression of a multi-stage centrifugal pump

As the urgency of the global energy crisis escalates and environmental protection standards become more stringent, the industrial sector is placing increased emphasis on enhancing energy efficiency and advancing vibration control technologies. Within this context, multi-stage centrifugal pumps (MSCPs), pivotal in energy systems, play a crucial role in influencing both system performance and environmental impact. This paper embarked on employing an inverse design method (IDM) to innovate the redesign of MSCP blades, introducing a steady-state index for characterizing the intensity of unsteady pressure fluctuations, thereby streamlining optimization costs. Optimization techniques utilizing an artificial neural network model and a multi-objective evolutionary algorithm were employed to achieve an optimal balance between maximizing energy efficiency and reducing hydro-induced vibrations. The optimized MSCP enhanced not only boosting performance but also a 2.75 % increase in weighted efficiency, significantly widening the high-efficiency operation zone. The improvement in vibration characteristics was manifested by an average reduction of more than 25 % in the amplitude of the primary frequency of pressure pulsations within the double volute, with a maximum reduction reaching 50.9 %. Furthermore, the research delved into the analysis of the internal energy dissipation mechanisms of MSCPs, drawing upon the entropy production theory and the enstrophy concept. This analysis reveals that energy dissipation in the mainstream zones is predominantly affected by shear enstrophy, whereas, in the wall regions, it is primarily governed by fluid velocity. The comprehensive performance enhancement of the optimized model is significantly credited to the refinement of the blade profile.

Inertial migration of rigid particles in shear-thinning fluids under asymmetric wall slip conditions

The determination of flow-induced equilibrium positions in pressure-driven flows in microchannels is of great practical importance in particle manipulation. In the computational analysis presented in this paper, the inertial ordering of neutrally buoyant rigid spheres in shear-thinning fluid flow through a hydrophobic microchannel is investigated. The combined effect of the viscosity index n of a power-law fluid and fluid slippage at the wall on the lateral focusing of microspheres is examined in detail. Using the finite element method, the Eulerian flow field between partially slipping parallel walls is simulated, and the Lagrangian movement of particles is continuously tracked. The Navier slip model is used to ensure a finite fluid velocity at the wall, and it is tuned by modifying the slip-length. It is observed that inertial particles concentrate at a standard equilibrium position of 0.6 times the channel half-width H, irrespective of fluid slip due to the symmetry of the flow field. However, this equilibrium position shifts closer to the walls as the viscosity index increases; for instance, when n = 0.5, particles stabilize at 0.75H. As a consequence of asymmetry in hydrodynamic behavior due to different fluid slippages at the upper and lower walls, the particle migration path is altered. In a channel with a no-slip upper wall and a partially slipping lower wall (β/H = 0.4), particles settle closer to the lower wall at 0.8H. Most importantly, the lateral movement of a particle released at a given vertical position can be altered by tailoring the wall hydrophobicity and viscosity index, thus enabling multiple equilibrium locations to be achieved.

Transient Shutdown Cooling Simulation of a Gas Turbine Test Rig Configuration Under Ventilated Natural Convection

Abstract A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aero-thermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead centre (BDC) and the top dead centre (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual grey body assumptions and Lambert?s law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup.

The stabilizing effect of temperature and magnetic field on a 2D magnetic Bénard fluids

In this paper we study the stability of a special magnetic Bénard system near equilibrium, where there exists Laplacian magnetic diffusion and temperature damping but the velocity equation involves no dissipation. Without any velocity dissipation, the fluid velocity is governed by the two-dimensional incompressible Euler equation, whose solution can grow rapidly in time. However, when the fluid is coupled with the magnetic field and temperature through the magnetic Bénard system, we show that the solution is stable. Our results mathematically illustrate that the magnetic field and temperature have the effect of enhancing dissipation and contribute to stabilize the fluid.

Cerebro-spinal flow pattern in the cervical subarachnoid space of healthy volunteers: Influence of the spinal cord morphology.

Toward further cerebro-spinal flow quantification in clinical practice, this study aims at assessing the variations in the cerebro spinal fluid flow pattern associated with change in the morphology of the subarachnoid space of the cervical canal of healthy humans by developing a computational fluid dynamics model. 3D T2-space MRI sequence images of the cervical spine were used to segment 11 cervical subarachnoid space. Model validation (time-step, mesh size, size and number of boundary layers, influences of parted inflow and inflow continuous velocity) was performed a 40-year-old patient-specific model. Simulations were performed using computational fluid dynamics approach simulating transient flow (Sparlart-Almaras turbulence model) with a mesh size of 0.6, 6 boundary layers of 0.05 mm, a time step of 20 ms simulated on 15 cycles. Distributions of components velocity and WSS were respectively analyzed within the subarachnoid space (intervertebral et intravertebral levels) and on dura and pia maters. Mean values cerebro spinal fluid velocity in specific local slices of the canal range between 0.07 and 0.17 m.s-1 and 0.1 and 0.3 m.s-1 for maximum values. Maximum wall shear stress values vary between 0.1 and 0.5 Pa with higher value at the middle of the cervical spine on pia mater and at the lower part of the cervical spine on dura mater. Intra and inter-individual variations of the wall shear stress were highlighted significant correlation gwith compression ratio (r = 0.76), occupation ratio and cross section area of the spinal cord. The inter-individual variability in term of subarachnoid canal morphology and spinal cord position influence the cerebro-spinal flow pattern, highlighting the significance of canal morphology investigation before surgery.

Influence of thermal radiation, viscous dissipation, and joule heating on entropy generation and flow of a Maxwell hybrid nanofluid over an exponentially stretching sheet with couple stress effects

Using a numerical technique, this study explores the flow and thermal aspects of a Maxwell hybrid nanofluid across an exponentially stretched sheet. The analysis incorporates the effects of thermal radiation, viscous dissipation, Joule heating, and chemical reaction. We use the in-built MATLAB function bvp4c to successfully solve the governing equations after we convert them to ordinary differential equations. The key novelty of this work lies in employing the Maxwell hybrid nanofluid, a more complex fluid than traditional nanofluids or regular Maxwell fluids and conducting a multifaceted analysis that considers factors like couple stress, chemical reaction, and entropy generation optimization alongside flow and heat transfer. The findings demonstrate that the Maxwell parameter and the magnetic field parameter both reduce fluid velocity due to opposing forces and enhanced elasticity, respectively. The temperature profile exhibits a rise with increasing thermal radiation, volume fraction of nanoparticles, and Eckert number due to enhanced radiative absorption, improved heat transfer, and internal heat generation respectively. As the Brinkman number and volume percentage of copper nanoparticles increase, the entropy generation becomes more intense and the Bejan number decreases as a result of enhanced viscous dissipation and friction. Between the values of 0.1 and 0.7 for Maxwell parameter, the friction factor exhibits a decrement of 0.1077. The Nusselt number, signifying heat transfer efficiency, reduces with the Eckert number but increases with the radiation parameter and volume fraction of nanoparticles. Between the values of 0.1 and 0.7 for Eckert number, the friction factor exhibits a decrement of 0.1077. Lastly, a steeper concentration gradient causes the Sherwood number, which is an indication of the mass transmission rate, to rise with the Schmidt number. it is detected that the rate of heat transfer increases at a rate of 0.0721 when chemical reaction values lie between 0 and 1.8.

Identification of the Problem in Controlling the Air–Fuel Mixture Ratio (Lambda Coefficient λ) in Small Spark-Ignition Engines for Positive Pressure Ventilators

The air–fuel ratio is a crucial parameter in internal combustion engines that affects optimal engine performance, emissions, fuel efficiency, engine durability, power, and efficiency. Positive pressure ventilators (PPVs) create specific operating conditions for drive units, characterized by a reduced ambient pressure compared to standard atmospheric pressure, which is used to control carburetor-based fuel supply systems. The impact of these conditions was investigated for four commonly used PPVs (with internal combustion engines) in fire services across the European Union (EU), using a lambda (λ), carbon dioxide (CO2), carbon monoxide (CO), and hydrogen carbon (HC) analyser for exhaust gases. All four ventilators were found to operate with lean and very lean mixtures, with their lambda coefficients ranging from 1.6 to 2.2. The conducted tests of the CO2, CO, and HC concentrations in the exhaust gases of all four fans show dependencies consistent with theoretical analyses of the impact of the fuel–air mixture on emissions. It can be observed that as the amount of burned air decreases, the values of CO and HC decrease, while the concentration of CO2 increases with the increase in engine load. Such an operation can accelerate engine wear, increase the emission of harmful exhaust gases, and reduce the effective performance of the device. This condition is attributed to an inadequate design process, where drive units are typically designed to operate within atmospheric pressure conditions, as is common for these engines. However, when operating with a PPV, the fan’s rotor induces significant air movement, leading to a reduction in ambient pressure on the intake side where the engine is located, thereby disrupting its proper operation.

A new reactor with porous baffle for thermochemical heat storage: Design and performance analysis

The Ca(OH)2/CaO reaction system presents broad development prospects for thermochemical heat storage. However, the poor thermal conductivity of heat storage material and the complex internal flow limit the performance of the reactor. To improve the performance of the reactor, this work designs a new improved fixed bed reactor with baffle. The comparison with and without baffle, as well as the effects of operation conditions and structural parameters of the improved reactor on heat storage and release performance, are numerically investigated. The results show that the improved reactor can enhance heat transfer and flow inside the reactor, resulting in performance improvement. After baffle installation, there is a 64% decrease in the pressure drop, a 29.14% reduction in the heat storage time, and a 35.45% reduction in the heat release time. Besides that, the improved reactor can maintain the high temperature for longer at the outlet during heat release. The orthogonal test design analysis reveals that the inlet velocity of direct heat transfer fluid has the greatest impact on heat storage, while the inlet velocity of indirect heat transfer fluid has the smallest impact, and the same applies to heat release. The thermal conductivity and permeability of the porous baffle have minor impacts, but the air distribution chamber has a noticeable influence. This work can guide the optimization design and operation adjustment of the reactor.

Applied Electric Field Effects on Diffusivity and Electrical Double-Layer Thickness.

This study utilizes molecular dynamics (MD) simulations and continuum frameworks to explore electroosmotic flow (EOF) in nanoconfined aqueous electrolytes, offering a promising alternative to conventional micro-/nanofluidic systems. Although osmotic behavior in these environments is deeply linked to local fluid properties and interfacial dynamics between the fluid and electrolyte solutions, achieving a complete molecular-level understanding has remained challenging. The findings establish a linear relationship between electric field strength and fluid velocity, uncovering two distinct transport regimes separated by a critical threshold, with a markedly intensified flow in the second regime. It is demonstrated that rising electric field strengths significantly enhance water diffusion coefficients, supported by a detailed analysis of fluid hydration structures, the potential of mean force (PMF), and local stress tensors. Due to the applied electric field strength, the motion of ions and water accelerates, leading to the redistribution of ions and intensification of electrostatic forces. This expands the thickness of the electric double layer (EDL) and amplifies fluid diffusivity, thereby enhancing nanoscale fluid activity. These insights enhance the molecular-level understanding of EOF and define the stability of flow regimes, providing valuable guidelines for advancing nanofluidic technologies, such as drug delivery systems and lab-on-a-chip devices.

Evaluation of physiological and thermal comfort effectiveness of ceiling fan and table fan during a heat wave

Heat waves are becoming a significant global concern as they have substantial repercussions on human health. Further, the adverse impact of heat waves on health will likely worsen globally. The use of electric fans is an energy-saving and sustainable cooling strategy against heat waves, but current health guidelines discourage fan use during heat waves. Previous research has shown that health guidelines underestimated the evaporative cooling impact of fans. These studies mainly focused on the effects of table fans on various physiological parameters of occupants in hot environments. Nevertheless, the air movement produced by both table fans and ceiling fans may influence the occupants’ physiological and perceptual responses significantly. Hence, the present study investigated the effectiveness of no-fan, table-fan and ceiling-fan conditions during heat waves through an experimental approach. Sixteen healthy young participants were exposed to an air temperature of 41.0 ± 0.5 °C and relative humidity of 35 ± 2 % for 2 hours. The participants’ physiological parameters and perceptual responses were collected. We found that both table and ceiling fans delay the changes in thermoregulatory and cardiovascular strain compared to the no-fan scenario. Moreover, table fans minimize physiological strain and provide greater comfort than ceiling fans. Hence, people should opt for table fans over ceiling fans during heat waves.

Hybrid ferrofluid flow on a stretching sheet with Stefan blowing and magnetic polarization effects in a porous medium

PurposeThis study investigates the behavior of viscous hybrid ferromagnetic fluids flowing through plain elastic sheets with the magnetic polarization effect. It examines flow in a porous medium using Stefan blowing and utilizes a versatile hybrid ferrofluid containing MnZnFe2O4 and Fe3O4 nanoparticles in the C2H2F4 base fluid, offering potential real-world applications. The study focuses on steady, laminar and viscous incompressible flow, analyzing heat and mass transfer aspects, including thermal radiation, Brownian motion, thermophoresis and viscous dissipation with convective boundary condition.Design/methodology/approachThe governing expression of the flow model is addressed with pertinent non-dimensional transformations, and the finite element method solves the obtained system of ordinary differential equations.FindingsThe variations in fluid velocity, temperature and concentration profiles against all the physical parameters are analyzed through their graphical view. The association of these parameters with local surface friction coefficient, Nusselt number and Sherwood number is examined with the numerical data in a table.Originality/valueThis work extends previous research on ferrofluid flow, investigating unexplored parameters and offering valuable insights with potential engineering, industrial and medical implications. It introduces a novel approach that uses mathematical simplification techniques and the finite element method for the solution.

Planck Dust Polarization Power Spectra Are Consistent with Strongly Supersonic Turbulence

The polarization of the cosmic microwave background is rich in information but obscured by foreground emission from the Milky Way’s interstellar medium (ISM). To uncover relationships between the underlying turbulent ISM and the foreground power spectra, we simulated a suite of driven, magnetized, turbulent models of the ISM, varying the fluid properties via the sonic Mach number, MS , and magnetic (Alfvén) Mach number, MA . We measure the power spectra of density (ρ), velocity (v), magnetic field (H), total projected intensity (T), parity-even polarization (E), and parity-odd polarization (B). We find that the slopes of all six quantities increase with MS . Most increase with MA , while the magnetic field spectrum steepens with MA . By comparing spectral slopes of E and B to those measured by Planck, we infer typical values of MS and MA for the ISM. As the fluid velocity increases, MS>4 , the ratio of BB power to EE power increases to approach a constant value near the Planck-observed value of ∼0.5, regardless of the magnetic field strength. We also examine correlation coefficients between projected quantities, and find that r TE ≈ 0.3, in agreement with Planck, for appropriate combinations of MS and MA . Finally, we consider parity-violating correlations r TB and r EB.

Forced convection heat transfer in AlSi7Mg lattice structures fabricated by additive manufacturing

The thermal-hydraulic performance of lattice structures with different topologies and relative densities was investigated. AlSi7Mg sandwich panels cored with vertical fin, pyramidal, and tetrahedral lattices were fabricated using additive manufacturing. Four different relative densities (7.5 %, 10 %, 12.5 %, and 15 %) were considered for each lattice core. The experiment was conducted under constant heat flux and steady-state forced convection. Results showed that increasing relative density led to an increase in the average Nusselt number by 3.2–12.5 % in the vertical fin, 23.8–56.4 % in the pyramidal lattice, and 38.8–46.9 % in the tetrahedral lattice. To evaluate the efficiency of different topologies, the average Nusselt number was compared at a fixed pumping power. The pyramidal lattice exhibited the best performance among the test samples, followed by the tetrahedral lattice. The numerical analysis was performed to gain further insights into the heat transfer mechanisms involved. As the relative density increased, an increase in both the maximum fluid velocity and turbulent kinetic energy was observed in all test samples. The numerical results demonstrate that the observed improvement in thermal-hydraulic performance with increasing relative densities in experiments is attributable to the enhanced momentum of the fluid and turbulent mixing.