Core Fluid Research Articles

Computational steady-thrust vector controlsupersonic secondary flow injection

This paper presents the Computational study of flow through the Rocket Nozzle in order to manoeuvre the Rocket by means of Supersonic Secondary Injection of Hot gases. Well-designed nozzles can accelerate these gases to speeds of thousands of meters per second. In addition to accelerating the gases, nozzles are often responsible for steering (or “vectoring”) the flow in order to control the rocket’s direction of flight. Due to continuous secondary injection of hot gases, the strong unsteady effects like Shear Layers, Intervention of Shockwaves with the Core fluid flow, Biased Wall Shear, etc., has to be studied precisely to appraise/evaluate the effectiveness of Nozzle contribution in role of steering the Rocket. Numerical Technique/Computational Analysis has been carried out to provide tons of insight about the meticulous behavior of Fluid particles while they interact with secondary flow. Comparative study on Supersonic Fluid Flow and the intervention of Secondary Injection of Hot gases has been carried at different angle of injection and at different injecting Pressure in order to find its optimum injection angle and optimum Injecting Pressure. It has been observed that Steering of Rocket drives well by Secondary Injection when its injecting angle becomes tangential to fluid flow direction and Injecting Pressure favors to steer the rocket when it increases its magnitude.

A new linearly unstable mode in the core-annular flow of two immiscible fluids

Abstract

Development of empirical models for the prediction of surface functional parameters in ultrasonic elliptical vibration cutting

Over the past decades, significant improvement has been witnessed in using 3D surface parameter characterization to study machined surfaces’ functional properties. However, the prediction and optimization of these valuable metrics under the influence of various cutting conditions have remained a significant concern. This paper focuses on modeling the effects of cutting speed, feed rate, depth of cut, and vibration amplitude on machining output responses in terms of 3D surface functional parameters, including surface bearing index (Sbi) and core fluid retention index (Sci). Ultrasonic elliptical vibration cutting (UEVC) experiments are performed to evaluate the variation trend of surface functional parameters while adopting the Taguchi analysis and response surface methodology (RSM) approach. The analysis results revealed that the cutting speed has the most significant impact on both (Sbi) and (Sci), followed by feed rate and vibration amplitude in varying rankings between responses; and lastly, the depth of cut, which exhibited the least effect. The validation test result indicated that the developed RSM predictive model was adequate in construction and verification. Finally, the output variables are optimized through the desirability function (CDF) approach. A comparative experimental analysis between conventional cutting (CC) and UEVC was performed under the optimized parameter setting. The comparison result revealed that the functional indices were substantially enhanced under the UEVC method.

Oscillatory thermal–inertial flows in liquid metal rotating convection

Abstract

Radiative MHD flow of hybrid nanofluid past a porous stretching cylinder for heat transfer enhancement

AbstractThe current study investigates heat transfer enhancement due to the radiative magnetohydrodynamics (MHD) flow of a hybrid nanofluid past a porous stretching cylinder under the influence of variable viscosity as well as suction. The nonlinear partial differential equations governing the proposed physical model are transformed into nonlinear ordinary differential equations by applying suitable similarity transformation. The scaled‐down system is solved numerically by the fourth‐order Runge–Kutta method along with shooting technique for the achievement of asymptotic boundary condition. The velocity and temperature profiles are obtained for various physical factors of the problem, namely, magnetic interaction factor , Reynolds number , volume fraction factor of copper , variable viscosity , and radiation factor , together with suction , by fixing the Prandtl number of the core fluid (ethylene glycol) constant at 25.825. The numerical values of skin friction and the rate of heat transfer are obtained and tabulated. To validate the proposed physical model, numerical simulations are provided with comparison. The paper highlights the effects of physical factors, namely, radiation, variable viscosity, and suction parameters, on the flow of a hybrid nanoflluid for heat transfer enhancement.

Aero Engine Concepts Beyond 2030: Part 2—The Free-Piston Composite Cycle Engine

Abstract Recognizing the attention currently devoted to the environmental impact of aviation, this three-part publication series introduces two new aircraft propulsion concepts for the timeframe beyond 2030. This second part presents the free-piston composite cycle engine concept. It is composed of a gas turbine topped with a free-piston system. The latter is a self-powered gas generator in which the internal combustion process drives an integrated air compressor. Here, several free-piston engines replace the high-pressure core of the gas turbine. Through the ability to work at much higher temperatures and pressures, the overall system efficiency can be increased significantly, and fuel burn as well as CO2 emissions reduce. The proposed free-piston composite cycle engine design is described in detail, and the sources of thermodynamic benefits are stated. Concrete engineering solutions consider the implementation into an aircraft. The free-piston design enables lower weight and size compared to a crankshaft-bound piston engine, as no mechanical transmission and lubrication system is required. The absence of a crankshaft and connecting rods eliminates reactive forces, reduces mechanical losses, and allows higher mean piston velocities. Facilitated through air lubrication, higher cylinder temperatures are viable. The reduction of heat losses enables cooling of the piston-cylinder with core fluid. The use of a sequential combustion chamber can enhance operability and tailor the production of NOx in low-altitude operation. A discussion of emissions affecting the environment shows the potential to reduce the climate impact of aviation.

Investigation of hybridized composite pressure vessel

Burst pressure is the vital parameter to be strong-minded for their design. Burst pressure is the pressure at which vessel crack and core fluid seep outs. A design shelterbound that ought to not be surpassed. Further than this pressure possibly willescort to mechanical fall foul of and enduring loss of pressure restraint. The present work is aimed in studying the pressure vessel (PV) made with composite material. During the study the PV is fabricated by glass fiber with 90O fiber angle and performed hydrostatic test. Later the same PV is modeled in Ansys and analyzed with various fiber angles to determine the failure by considering their deformation, stress and strain of the PV using GFRP, CFRP and hybrid composites. At last the results obtained are validated.

Correlation of the tribological properties of LIPSS on TiN surface with 3D parameters of roughness

The relationships between friction coefficients and 3D spatial roughness parameters, such as Sci (surface core fluid retention index), Svi (surface valley fluid retention index) and Sbi (surface bearing index), have been investigated for the laser-induced periodic surface structures (LIPSS) on the TiN coatings. Two types of the surface structures (cross-like and parallel ones) with different roughness levels were obtained using a fs-laser. It has been shown that the proposed roughness parameters correlate with the friction coefficients measured for the LIPSSs.

Radiative 3D-MHD flow of an aqueous ethylene glycol nanofluid past a two-way exponentially extending lamina

An analysis has been carried out for the radiative MHD flow of an aqueous ethylene glycol nanofluid past a two-way exponentially extending lamina. Appropriate transformation is used to reduce the nonlinear partial differential system to an ordinary differential system. The resulting nonlinear ordinary differential system is solved numerically using fourth order Runge Kutta shooting method for the satisfaction of asymptotic boundary condition. The velocity and temperature sketches of copper and alumina in aqueous ethylene glycol (a-EG) nanofluid for the present physical stratum are obtained and displayed graphically by fixing various values for pertinent factors of the problem namely, velocity ratio factor (λ), magnetic interaction factor (M), nanoparticle volume fraction (φ), exponential coefficient factor(A) and temperature-radiation factor (Rd) fixing the Prandtl number of the core fluid (a-EG) constant at 25.825 skin friction coefficient and rate of heat transfer for various factors of the problem are tabulated and compared with the existing results in the literature. Finally numerical simulation with comparisons is provided to demonstrate the effectiveness of the obtained result.

A novel suspension transport method: Viscoplastic lubrication of high-density fluids

We present proof-of-concept experiments to illustrate the application of viscoplastic lubrication in transport of high-concentration suspensions. The proposed transport method appears robust for a wide range of suspension concentrations. We develop a theoretical description of the flow that incorporates the significant density difference between the suspension and the lubricating fluid. We explore the variation of the pressure gradient and the flow rate ratio with fluid properties and demonstrate that buoyancy effects expand the favorable lubrication regime within the phase space of the problem. We illustrate the possibility of flow reversal in the core fluid and the emergence of a new flow regime, two features not captured when buoyancy stresses are neglected. • Viscoplastic lubrication of suspensions is proposed as a method to enhance transport. • Proof-of-concept experiments show transport of titania suspension with concentration 30–70 wt%. • Theoretical estimates of the flow field are developed to reveal buoyancy effects. • When buoyancy is sufficiently strong, flow reversal is observed in the core fluid. • Buoyancy can augment the favorable lubrication regime.

Forecasting yearly geomagnetic variation through sequential estimation of core flow and magnetic diffusion

Earth’s internal magnetic field is generated through motion of the electrically conductive iron-alloy fluid comprising its outer core. Temporal variability of this magnetic field, termed secular variation (SV), results from two processes: one is the interaction between core fluid motion and the magnetic field, the other is magnetic diffusion. As diffusion is widely thought to take place over relatively long, millennial time scales, it is common to disregard it when considering yearly to decadal field changes; in this frozen-flux approximation, core fluid motion may be inferred on the core–mantle boundary (CMB) using observations of SV at Earth’s surface. Such flow models have been used to forecast variation in the magnetic field. However, recent work suggests that diffusion may also contribute significantly to SV on short time scales provided that the radial length scale of the magnetic field structure within the core is sufficiently short. In this work, we introduce a hybrid method to forecast field evolution that considers a model based on both a steady flow and diffusion, in which we adopt a two-step process: first fitting the SV to a steady flow, and then fitting the residual by magnetic diffusion. We assess this approach by hindcasting the evolution for 2010–2015, based on fitting the models to CHAOS-6 using time windows prior to 2010. We find that including diffusion yields a reduction of up to 25% in the global hindcast error at Earth’s surface; at the CMB this error reduction can be in excess of 77%. We show that fitting the model over the shortest window that we consider, 2009–2010, yields the lowest hindcast error. Based on our hindcast tests, we present a candidate model for the SV over 2020–2025 for IGRF-13, fit over the time window 2018.3–2019.3. Our forecasts indicate that over the next decade the axial dipole will continue to decay, reversed-flux patches will increase in both area and intensity, and the north magnetic (dip) pole will continue to migrate towards Siberia.

Radiation force and torque on a two-dimensional circular cross-section of a non-viscous eccentric layered compressible cylinder in acoustical standing waves

The purpose of this study is to develop an analytical formalism and derive series expansions for the time-averaged force and torque exerted on a compound coated compressible liquid-like cylinder, insonified by acoustic standing waves having an arbitrary angle of incidence in the polar (transverse) plane. The host medium of wave propagation and the eccentric liquid-like cylinder are non-viscous. Numerical computations illustrate the theoretical analysis with particular emphases on the eccentricity of the cylinder, the angle of incidence and the dimensionless size parameters of the inner and coating cylindrical fluid materials. The method to derive the acoustical scattering, and radiation force and torque components conjointly uses modal matching with the addition theorem, which adequately account for the multiple wave interaction effects between the layer and core fluid materials. The results demonstrate that longitudinal and lateral radiation force components arise. Moreover, an axial radiation torque component is quantified and computed for the non-absorptive compound cylinder, arising from geometrical asymmetry considerations as the eccentricity increases. The computational results reveal the emergence of neutral, positive, and negative radiation force and torque depending on the size parameter of the cylinder, the eccentricity, and the angle of incidence of the insonifying field. Moreover, based on the law of energy conservation applied to scattering, numerical verification is accomplished by computing the extinction/scattering energy efficiency. The results may find some related applications in fluid dynamics, particle trapping, mixing and manipulation using acoustical standing waves.

Magnetic boundary layers in numerical dynamos with heterogeneous outer boundary heat flux

It has been proposed that magnetic flux expulsion due to outer core fluid upwellings may affect the geomagnetic secular variation on the core-mantle boundary (Bloxham, 1986). In this process intense horizontal field lines are concentrated below the outer boundary, introducing small radial length scales and consequently strong radial diffusion. Here we explore such magnetic boundary layers in numerical dynamo simulations with heterogeneous outer boundary heat flux inferred from a tomographic model of lower mantle seismic shear waves velocity anomalies. Our scheme associates magnetic boundary layers to peak horizontal magnetic fields at the top of the shell. In our models mean magnetic boundary layer thickness ranges ≈200 − 400 km and decreases with increasing magnetic Reynolds number. Extrapolation or interpolation to Earth's core conditions based on total core flow amplitude or its poloidal part gives mean magnetic boundary layer thickness of ≈220 and ≈260 − 330 km, respectively. We find magnetic boundary layers associated with the azimuthal field at the equatorial region, whereas magnetic boundary layers associated with the meridional field are found at mid latitudes. Negative outer boundary heat flux anomalies yield preferred locations of expulsion of azimuthal field below Africa and the Pacific, while positive outer boundary heat flux anomalies yield preferred locations of expulsion of meridional field below the Americas and East Asia. Furthermore, we find a tendency of the azimuthal field to low latitudes of the Northern Hemisphere. Our results suggest that the local diffusion time is on the order of several kyr and the local magnetic Reynolds number is on the order of ≈10, both much smaller than classical estimates.

Surrogate modelling of transient stratified flow in a u-shaped pipe

In this work, we compute the mixed convection flow through a u-shaped bend, where transient thermal boundary conditions are applied at the inlet. The flow is governed by the Unsteady Reynolds Averaged Navier-Stokes equations. The Reynolds number is set to 10 000, while the Prandtl number is 6 (water). Polynomial chaos with parametric space discretisation is employed to assess the influence of Froude number (Fr), related to the magnitude of the thermal transient, uniformly distributed over a range of Fr=0.402 to 0.938. Skewed and bi-modal responses in the strength of the stratification were observed, which are related to the flow being at locally sub-critical or supercritical Fr.The application of polynomial expansion enables wider exploration of parameter space to gain better understanding of flow behaviour. For Fr<0.67, we observe a more persistent thermal stratification as the secondary flow motion confines the hotter core fluid to the centres of the two counter-rotating vortices away from the pipe wall.

Study on Variation Laws of Fluid Threshold Pressure Gradient in Low Permeable Reservoir

A study on the seepage characteristics and laws of nano-micron pore throat in a low permeable reservoir matrix is of great significance for promoting high efficacy of low permeable reservoirs. Threshold pressure gradient (TPG) is an essential factor to reflect the seepage law. Here, variation laws of TPG and its influencing factors of low reservoir fluid are analyzed systematically through physical simulation experiment. Throat diameter distribution of cores was measured by a mercury injection method, and it was found that with the decrease of pore throat median diameter, TPG increase appeared slowly first and fast afterwards. The patterns of the TPG with permeability in water and oil were compared. Results showed that the TPG versus permeability gave power functions in a form and the TPG in oil was more than two times larger than that of water. Besides, TPG in two-phase flow was investigated by the stabilization method. Tests revealed that the higher the oil saturation, the greater the TPG value, and the TPG in two-phase flow is always higher than that of single-phase flow under the same conditions, which function as the combined action of the capillary force. In addition, the effects of core length, fluid type, and core wettability on the TPG were studied systematically, which has guiding significance for the development of a low permeability reservoir.

Experimental investigation on surface functional indices in Ultrasonic Elliptical Vibration Cutting of C45 carbon steel

The tribological performance of a machined surface is greatly influenced by the quality and reliability of manufacturing processes employed in its creation. In the present study, an attempt has been made to investigate the effects of various cutting parameters which include cutting speed, feed rate, depth of cut, and ultrasonic vibration amplitude on surface tribological characteristics of C45 carbon steel while employing surface functional indices, namely, Surface bearing index (Sbi), Core fluid retention index (Sci), and Valley fluid retention index (Svi). Ultrasonic elliptical vibration-assisted turning (UEVT) and conventional turning (CT) experiments were carried out to comparatively assess the performance of both cutting methods in terms of the surface functional parameters’ response. The observed variations of the surface functional indices under the influence of the investigated cutting parameters were critically analyzed, and a detailed comparative discussion based on the surface generation mechanisms of both cutting methods is presented. The results obtained from the 3D surface measurement revealed that the variation trends of the surface functional indices in both processing techniques are relatively the same and the UEVC method was found to have higher potential of improving the overall tribological properties of the machined surface compared with the CC method.

Weak magnetic field changes over the Pacific due to high conductance in lowermost mantle

For the past few centuries, the temporal variation in the Earth's magnetic field in the Pacific region has been anomalously low. The reason for this is tied to large scale flows in the liquid outer core near the core-mantle boundary, which are weaker under the Pacific and feature a planetary scale gyre that is eccentric and broadly avoids this region. However, what regulates this type of flow morphology is unknown. Here, we present results from a numerical model of the dynamics in Earth's core that includes electromagnetic coupling with a non-uniform conducting layer at the base of the mantle. We show that when the conductance of this layer is higher under the Pacific than elsewhere, the larger electromagnetic drag force weakens the local core flows and deflects the flow of the planetary gyre away from the Pacific. The nature of the lowermost mantle conductance remains unclear, but stratified core fluid trapped within topographic undulations of the core-mantle boundary is a possible explanation.

Predictive value of a CLIA-approved organoid based drug sensitivity test.

3630 Background: Precision medicine integrates genetic, molecular, and clinical information to optimize therapy selection for cancer patients. Ex vivo drug testing has the potential to match the right drug to the right patient. We developed a CLIA-certified functional drug assay for all solid tumors which provides an actionable report of organoid sensitivity to targeted, endocrine and chemotherapy agents as a tool for therapeutic decisions. Objectives: To establish the predictive power of the test in relation to well-known genomic biomarkers as well as prior treatments to identify drug sensitivity. To demonstrate that functional drug testing increases the actionability of genomic reports. Methods: From 2016 to 2019, 240 organoids from cancer patients were subjected to functional testing at SEngine Precision Medicine. Patients with advanced primary or metastatic cancer (solid tumors) who were treatment naïve or had previous therapies fail. Fresh samples of tumor cells from core biopsies, surgical excisions, or fluids arrived &lt;48 hrs following collection and were cultured as 3D organoids. They were evaluated using a multi-dose response format with a library of up to 130 compounds. Drug sensitivity was quantified using a score that combines sensitivity and personalization of each patient’s response relative to a reference population. Known genomic actionability from levels of evidence 1-2 from MSKCC OncoKB were queried against results for correlation. Results: Organoids were derived from breast (18.7%), ovarian (18.3%), colorectal (17.9%), pancreatic (6.7%), and others solid tumors (38,3%). Median age of patients was 53 (r5-83). 68 drugs on average were tested per patient with a mean turnaround time of 18 days (r9 -37). A mean of 7 drugs per patient were identified as top scoring drugs. In 75 patients with genomic data, we found high concordance of drug sensitivity with known genomic anchors (e.g., inhibitors of BRCA1/ PARP, ERBB2/HER2, FGFR1-2/FGFR, KRAS, PIK3CA/PI3K), measured as sensitivity to drugs among this targeted groups. However, several patient samples demonstrated sensitivity to targeted agents in the absence of known genomic biomarkers. Most important, analysis of previous treatments indicated &gt;90% of retrospective concordance. Conclusions: Organoid based drug testing exhibits strong concordance with genomic and retrospective clinical evidence. In addition, functional testing identifies candidate therapies in patients with no known biomarkers and can identify the significance of variants currently not validated.

Disruption of Electrospinning due to Water Condensation into the Taylor Cone.

The well-known problems of electrospinning hygroscopic polymer fibers in humid air are usually attributed to water condensing onto the jet mid-flight: water enters the jet as an additional solvent, hindering solidification into well-defined fibers. Here, we show that fiber fusion and shape loss seen at the end of the process may actually stem from water already condensing into the Taylor cone from where the jet ejects, if the solvent is volatile and miscible with water, for example, ethanol. The addition of water can radically change the solvent character from good to poor, even if water on its own is an acceptable solvent. Moreover, and counterintuitively, the water condensation promotes solvent evaporation because of the release of heat through the phase transition as well as from the exothermic mixing process. The overall result is that the polymer solution develops a gel-like skin around the Taylor cone. The situation is significantly aggravated in the case of coaxial electrospinning to make functional composite fibers if the injected core fluid forms a complex phase diagram with miscibility gaps together with the polymer sheath solvent and the water condensing from the air. The resulting phase separation coagulates the polymer throughout the Taylor cone, as liquid droplets with different compositions nucleate and spread, setting up strong internal flows and concentration gradients. We demonstrate that these cases of uncontrolled polymer coagulation cause rapid Taylor cone deformation, multiple jet ejection, and the inability to spin coaxial fiber mats, illustrated by the example of coaxial electrospinning of an ethanolic polyvinylpyrrolidone solution with a thermotropic liquid crystal core, at varying humidities.

Numerical simulation of pharyngeal bolus flow influenced by bolus viscosity and apparent slip.

Pharyngeal bolus flow was simulated numerically using a finite element method. The bolus liquids were X-ray medium, glucose, and thickener solutions. For a low-viscosity bolus, the simulation showed a reasonable agreement of bolus velocity with X-ray measurements. The influence of bolus density on swallowing velocity was investigated numerically. Although a higher density resulted in a higher bolus velocity, the increase in velocity was modest. When the bolus viscosity was high, it was necessary to apply the slip boundary condition to obtain an agreement for bolus velocity between the simulation and X-ray measurements. The simulations also showed that the method of characteristic shear rate proposed by Zhu et al., Journal of Texture Studies, 2014, 45, 430-439 is effective for predicting the bolus velocity for shear-thinning fluids. In order to discuss the effect of saliva lubrication and the physical meaning of the characteristic shear rate, an immiscible two-layer flow of the core and wall layer was analyzed theoretically by analogy with mesopharyngeal bolus flow. The characteristic shear rate enabled us to correlate the macroscopic flow behavior and the viscosity of the core layer fluid. Lubrication due to the wall layer caused the apparent slip and enhanced the transfer of viscous core fluid. For viscous fluid that presented a large apparent slip in the two-layer model, the slip boundary condition was needed in the swallowing simulation. The numerical simulation and model flow analysis revealed the usefulness of characteristic shear rate and the importance of saliva-layer lubrication in swallowing.