Pressure Region Research Articles

PROPELLER INFLUENCE ON SURFACE PRESSURE FLUCTUATION UNDER BOUNDARY LAYER INGESTION CONDITION

Research on propeller noise under boundary layer ingestion condition is essential for designing new aircraft concepts. Measurements of pressure spectra on a flat plate below a propeller give important information about the noise coming from the blades. These also are important for designing surface noise mitigation structures, such as acoustic black holes, meta-materials, and liners. This paper investigates the effects of a propeller on the flat plate surface pressure under boundary layer ingestion, using bottom of the wind tunnel channel as flat plate. Tripping devices on the wind tunnel bottom wall control the boundary layer thicknesses. The surface pressure is measured using an instrumented plate positioned underneath the propeller. The plate has 87 pressure taps to measure the unsteady and steady pressure using the remote microphone probe (RMP) technique. The results show the influence of the propeller inflow, the advance ratio, and the number of blades on the different regions underneath the propeller, and on coherent turbulent structures of the incoming flow. The boundary layer thicknesses affects the static pressure upstream of the propeller - creating high pressure regions. The propeller affects the turbulent structures downstream of the blades, increasing its correlation length.

Dense Monolayer Network Structures of Double Hydrophilic Hyperbranched Copolymers at the Air/Water Interface.

Influences of subphase pH and temperature on the interfacial aggregation behavior of two double hydrophilic hyperbranched copolymers of poly[oligo(ethylene glycol) methacrylate-co-(2-diisopropylamino)ethyl methacrylate] (P(OEGMA-co-DIPAEMA)) at the air/water interface are studied by the Langmuir film balance technique. Morphologies of their Langmuir-Blodgett (LB) films are characterized by atomic force microscopy (AFM). At the interface, P(OEGMA-co-DIPAEMA) copolymers tend to form a dense network structure of circular micelles composed of branching agent-connected carbon backbone cores and mixed shells of OEGMA and DIPAEMA segments (pendant groups). This network structure containing many honeycomb-like holes with diameters of 6-8nm is identified for the first time and clearly observed in the enlarged AFM images of their LB films. Under acidic conditions, surface pressure versus molecular area isotherms of the two copolymers in the low-pressure region show larger mean molecular area than those under neutral and alkaline conditions due to the lack of impediment from DIPAEMA segments. Upon further compression, each isotherm exhibits a wide pseudo-plateau, which corresponds to OEGMA segments being pressed into the subphase. Furthermore, the isotherms under neutral and alkaline conditions exhibit the lower critical solution temperature behavior of OEGMA segments, and the critical temperature is lower when the hyperbranched copolymer contains higher OEGMA content.

Turbulence intensity effect on axial-flow-induced vibration of a two-cylinder cluster

This numerical study aims to investigate the effect of inlet turbulence intensity Tu (0.05 – 5.0%) on flow-induced vibration of an elastic cylinder with fixed ends placed next to a rigid cylinder of the same diameter and length in axial flow. Turbulent flow structure and fluid-structure interaction are captured using large eddy simulation and two-way coupling calculation, respectively. It is found that Tu produces a pronounced effect on vibration characteristics of the elastic cylinder. Given a dimensionless velocity U̅ (i.e., 3.49, less than critical U̅ for onset of buckling), root-mean-square vibration amplitude Arms⁎ increases rapidly with increasing Tu from 0.7% to 5.0% for any given center-to-center cylinder spacing P⁎ (1.20 – ∞). This change in Arms* is attributed to the interactions between turbulent structures of different scales, where interactions between large-scale eddies result in the formation of small-scale eddies in the interstitial flow between the cylinders, thus enhancing greatly the flow instability and hence Arms*. Another interesting phenomenon takes place at U̅ = 7.62 (beyond the critical U̅ for onset of buckling) and P⁎ = 1.80, where the elastic cylinder buckles into a new dynamic equilibrium state. As Tu increases from 0.3% to 1.5%, the flutter instability occurs merely along the y direction that is normal to the plane of two cylinders axes and also normal to main stream direction. It has been found that the high-Tu flow triggers two vortices in this direction, giving rise to two regions of different pressures around the cylinder. The two regions reposition quasi-periodically themselves, thus producing lateral forces that account for this flutter instability in the y direction. Scaling analysis of the dependence of Arms⁎ on Tu and U̅ reveals that the relationship Arms⁎ = g1(Tu, U̅) may be reduced to Arms⁎ = g2(U̅eff); g1 and g2 are different functions and the scaling factor U̅eff = U̅ TF, where TF is the turbulence factor that accounts for the effect of Tu on Arms⁎. The scaling law is discussed in detail, along with the physical meanings of U̅eff.

Utilizing an Ultrasonic Inspection System Operating Inside an Autoclave and Machine Learning to Quantify Porosity within Composites During Cure

ABSTRACT Composite materials are increasingly being utilized in aerospace applications for their high stiffness and strength to weight ratios and fatigue resistance. However, defects in the composite may arise during cure (e.g. porosity, delamination, fiber waviness), and current technology only allows for post-cure evaluation (e.g. microscopy, ultrasonic inspection). A high-temperature ultrasonic scanning system was developed for deployment in an autoclave, which can detect porosity in composites during the cure process. This study focused on the implementation of machine learning techniques to help generate a model that can quantify porosity, in addition to detection and localization that has previously been demonstrated. Two, six-hour-long experiments were conducted on curing of 762 mm × 305 mm (30 in. ×12 in.) composite panels with a [0/45/90/-45]4s layup and varying regions of high and low pressure due to its tapered geometry in contact with a flat caul plate. The first experiment utilized a thick (12.7 mm) caul plate and the second utilized a thin (3.2 mm) caul plate. During experimentation, within the scan area (406 mm × 13 mm), data was recorded and stored for ultrasonic amplitude. Additional variables were measured or predicted including temperature, autoclave pressure, number of plies, slope of the composite panel surface with respect to the transducer, viscosity, and glass transition temperature. The pre-processed data was entered into the Regression Learner Application in MATLABⓇ,1 and a rational quadratic Gaussian process regression (GPR) was chosen for the machine learning algorithm. The model was then trained on a larger data set to make it more robust and capable of predictions using a function callout. The result was a machine learning algorithm that can reliably quantify porosity in a composite panel during cure based on measured amplitude response and generate images for intuitive visualization. This tool can be further trained with more experimentation and potentially employed for real-time porosity detection and quantification of composite components during cure in an autoclave. Practical use of this technology is the potential to dynamically control processing parameters (e.g. autoclave pressure) in real-time to reduce the level of porosity within the laminate to acceptable limits (e.g. 2% by volume).

LES and experimental investigation of flow field in the cyclone separator at different temperatures

The present study is aimed to investigate the effect of temperature on the flow field. In this study, LES (large eddy simulation) and HWA (hot wire anemometry) are used to investigate the time-averaged and instantaneous flow field in the cyclone at different temperatures. The numerical results agree well with the experiment data. The results show that temperature has an impact on both the time-averaged flow field and the fluctuations of the flow field. To investigate the effect of temperature on flow field fluctuations, we first reveal the mechanism of flow field fluctuations. The effect of temperature on vortex motion and tangential velocity fluctuation is analyzed, and a mathematical model for predicting the freqeuncy of vortex core precession at different temperatures is proposed, fT/f0=k(T0/T)0.125(1+m). The Q criterion is used to identify the vortex in the cyclone. When the temperature is high, the vortex core undergoes a typical vortex breakdown phenomenon at the lower part of the cyclone separator: the vortex core breaks up into a double helix shape. This is the reason for the disappearance of the negative pressure region, the decrease in tangential velocity and the weak fluctuation of tangential velocity in the dipleg at high temperature.

A Conjoined Rectilinear Collision Cell and Pulsed Extraction Ion Trap with Auxiliary DC Electrodes.

Ion traps are routinely directly coupled to mass analyzers, where they serve to suitably cool and shape an ion population prior to pulsed extraction into the analyzer proper. Such devices benefit from high duty cycle and transmission but suffer slow ion processing times caused by a compromise in the buffer gas pressure range that suitably dampens the ion kinetic energy without causing excessive scatter during extraction or within the analyzer. A rectilinear RF quadrupole ion trap has been characterized, conjoining a pressurized collision region with a pumped extraction region, and an unbroken RF interface for seamless ion transfer between them. Auxiliary electrodes mounted between the RF electrodes provide DC voltage gradients that serve to both guide ions through the device and position them at the extraction slot. The influence of the auxiliary DC upon the trapping RF field was measured, and suitable parameters were defined. A mode of operation was developed that allowed parallel processing of ions in both regions, enabling a repetition rate of 200 Hz when the device was coupled to a high-resolution accurate-mass analyzer.

Dynamic fracture of metal rods under overdriven effect of cylindrical detonation collision

AbstractThe collision of detonation waves is widely used in weapon design due to its ability to efficiently achieve an ultra‐high pressure region. This work discusses the dynamic fracture of metal rods under the collision of cylindrical detonations. In the experiments, the detonation wave collision is generated by detonating an explosive charge at its end position along two parallel initiation lines, which are detonated by a plane wave generator. The recovered metal rods were broken around their centers due to the superposition of detonation waves. A blue oxidation zone appeared at the fracture surfaces of steel rods in the contact zone under the charge, indicating the local existence of high temperatures. A finite element model was used to simulate and describe the dynamic fracture of metal rods caused by detonation wave collision. The three‐shock theory was used to examine the detonation wave collision. When the incidence angle was between 0° and 40°, the reflected shock wave pressure was approximately 2.1 times the CJ pressure. At an incidence angle of 44.84°, the ratio of Mach and CJ pressure reached a maximum of 3.1. The concentration degree of detonation pressure was developed to evaluate the superposition influence on the dynamic fracture of metal rods. The microstructure of fracture surfaces revealed that metal rods preferred shear fracture under high pressure concentration. With a low degree of pressure concentration, a brittle fracture may emerge. This research serves as a guide for designing and evaluating multimode warheads.

Electron-Beam Processing of Aluminum-Containing Ceramics in the Forevacuum Pressure Range

Aluminum–ceramic materials based on Al2O3 and AlN are widely used in the electronics industry and, according to a number of electrophysical and technical and economic parameters, are among the most suitable for the production of electrical and radio engineering products. In this study, it is shown that the treatment of ceramics based on Al2O3 with an electron beam with a power of 200–1100 W and a current of 10–50 mA leads to heating of the ceramic surface to a temperature of 1700 °C. When heated to a temperature of 1500 °C and kept at this temperature for no more than 10 s, an increase in the roughness of the ceramic surface is observed by more than an order of magnitude. At the same time, for ceramic substrates based on aluminum nitride, an increase in the temperature of electron beam treatment from 1300 to 1700 °C leads to an increase in thermal conductivity from 1.5 to 2 times. The edge angle of water wetting of the AlN surface can vary from 20 to 100 degrees depending on the processing temperature, which allows one to control the transition of the material from a hydrophilic to a hydrophobic state. At the same time, electron beam exposure to Al2O3 does not change the wettability of this material so much. Electron beam processing in the forevacuum pressure region allows controlled changes in the electrophysical properties of ceramic materials based on Al2O3 and AlN.

CO2 competes with radioactive chemicals for freshwater recovery: Hydrate-based desalination

Here, we introduce CO2 hydrate-based desalination (CHBD) technology for freshwater recovery from radioactive wastewater, for water particularly containing Cs and Sr. The hydrate equilibrium curves of CO2 hydrates shift towards lower temperature and higher pressure regions as the concentrations of CsCl and SrCl2 increase. X-ray diffraction and Raman spectroscopy measurements found that neither CsCl nor SrCl2 can affect the structure of CO2 hydrates. The high-pressure micro-differential scanning calorimetric results demonstrate that CO2 hydrates in the presence of CsCl and SrCl2 started to dissociate at lower temperatures due to the enrichment of CsCl and SrCl2 in the remaining solutions. The formation kinetics results indicate that increases in the concentrations of the radioactive chemicals lead to a decrease in the initial reaction rate and sub-cooling temperature. Solid-state nuclear magnetic resonance spectroscopy was utilized to confirm the exclusion of radioactive isotopes from solid gas hydrates. Importantly, the CHBD technology proposed in this study is applicable to radioactive wastewater containing Cs+ and Sr2+ across broad concentration ranges, spanning from a percent to hundreds of parts per million (ppm), and even sub-ppm levels, with comparable recovery efficiency. This study presents new insights into the potential of environmentally sustainable technologies to overcome the challenges posed by radioactive wastewater.

Enhancement of piezoelectric energy harvesting by the elliptical cylinder interference

The performance of the piezoelectric energy harvester (PEH) driven by a single bluff body is not entirely satisfactory in wind environment. However, the wake excitation generated by the interference cylinder can intensify the vibration and subsequently increase the harvested energy. This paper presents a piezoelectric energy harvester which uses an elliptical cylinder for interference (ECI). The extended Hamilton’s principle and the Gauss’s law is applied to obtain the electro-mechanical coupling model. Following this, the analytical solution is derived by employing the Galerkin procedure. Experiments pertaining to this study were conducted in a DC wind tunnel, where ECIs of varying aspect ratios were positioned directly upstream of the PEH. The experimental results not only verify the model accuracy, but also identify the distance between the ECI and the bluff body in terms of the proximity interference region, induced galloping region, and wake interference region. Only when the system is located in the induced galloping region, does the harvester’s output power significantly increase and the system stability improve. Furthermore, as the aspect ratio of the elliptical cylinder decreases, the harvested energy increases, and when the wind speed reaches 18 m/s, with the aspect ratio and the spacing ratio being 0.4 and 13 respectively, the harvester can yield a power density of 10.93 kW/m3. This is 624% higher than that without wake excitation. Numerical simulations demonstrate that the wake, generated by ECI, interferes with the positive pressure region in front of the funnel-shaped bluff body. This interference shifts the location of the positive pressure region to the sides of the bluff body and reduces its area.

A Temperature-Controlled Apparatus for Gas Permeability under Low Gas Pressure

The measurement of soil gas permeability is influenced by the temperature and pressure fluctuation in the low gas pressure region. In order to investigate these influences, a soil temperature-controlled apparatus connected to a low-gas-pressure supply equipment is proposed in this study. The low constant gas pressure is supplied by two Mariotte bottles, by which the airflow rate is measured. Meanwhile, the soil specimen is controlled by a temperature-controlled apparatus. During the test, the negative pore water pressure and volume change of the soil specimen are measured. Through the temperature-controlled apparatus, it is observed that as the temperature increases from 25 °C to 60 °C, there is a corresponding increase in soil sample porosity by 5.4%, while the negative pressure of pore water decreases by 11.1%. This can be attributed to the reduction in the surface tension of contractile skin caused by elevated temperatures. Furthermore, due to variations in gas viscosity with temperature, there was a significant decrease in the gas flow rate by 50.5%. And, the relationship between permeability and volumetric gas content at different temperatures in low-pressure regions well confirms the existing power-law model. In addition, the existence of a temperature-independent critical negative pore water pressure is observed, beyond which the intrinsic permeability remains constant. At 36 kPa of negative pore water pressure, the intrinsic permeability at 60 °C exhibits an 81.8% reduction compared to that at 25 °C. This decline in intrinsic permeability can be attributed to a diminished pore connectivity, resulting from elevated temperatures.

A multifunctional hydrogel-based strain sensor and triboelectric nanogenerator for running monitoring and energy harvesting

Recently, flexible wearable electronics for human running posture monitoring and human energy harvesting have attracted widespread attention. Hence, we design a mixed type conductive hydrogel based on polyvinyl alcohol, cotton paper, graphite oxide, and MXene, named PCGM hydrogel. Furthermore, the PCGM hydrogel can act as the PCGM-based strain sensor and triboelectric nanogenerator (P-TENG) for running posture monitoring and mechanical energy harvesting. The PCGM-based strain sensor has two sensing linear regions: The pressure sensitivity is 0.0164 kPa−1 in the low pressure region (0–16 kPa), whereas it is 0.002 86 kPa−1 in the high pressure region (16–120 kPa). To achieve comprehensive health monitoring of runners, the PCGM-based strain sensors can be installed on human joints and facial skin to monitor human posture and facial expressions. The PCGM hydrogel can be combined with a polytetrafluoroethylene film to form a P-TENG device for mechanical energy harvesting. The P-TENG maximum output power can reach 135 µW with a 30 MΩ load. The short-circuit current (Isc), open-circuit voltage (Voc), and transfer charge (Qsc) of P-TENG can reach 10.36 µA, 229.85 V, and 49.24 nC, respectively. This research provides an effective approach for human-running motion monitoring by using multifunctional flexible devices.

Manipulation of nonlinear optical responses in layered ferroelectric niobium oxide dihalides

Realization of highly tunable second-order nonlinear optical responses, e.g., second-harmonic generation and bulk photovoltaic effect, is critical for developing modern optical and optoelectronic devices. Recently, the van der Waals niobium oxide dihalides are discovered to exhibit unusually large second-harmonic generation. However, the physical origin and possible tunability of nonlinear optical responses in these materials remain to be unclear. In this article, we reveal that the large second-harmonic generation in NbOX2 (X = Cl, Br, and I) may be partially contributed by the large band nesting effect in different Brillouin zone. Interestingly, the NbOCl2 can exhibit dramatically different strain-dependent bulk photovoltaic effect under different polarized light, originating from the light-polarization-dependent orbital transitions. Importantly, we achieve a reversible ferroelectric-to-antiferroelectric phase transition in NbOCl2 and a reversible ferroelectric-to-paraelectric phase transition in NbOI2 under a certain region of external pressure, accompanied by the greatly tunable nonlinear optical responses but with different microscopic mechanisms. Our study establishes the interesting external-field tunability of NbOX2 for nonlinear optical device applications.

Experimental research on self-initiation process of rotating detonation wave by high-temperature ethylene-rich gas

This study investigates an experimental process of high-temperature ethylene-rich gas and air for rotating detonation. After abandoning the pre-detonator method, the high-temperature ethylene-rich gas was injected and collided with the outer wall to create a localized high temperature and pressure region that ignited the gas mixture to form the deflagration state. Whether it is a single deflagration flame or double deflagration flame, it is eventually transformed through the deflagration-to-detonation transition (DDT) process into a double detonation wave. With propagation and collision of the double waves, the injection pressure increases, which results in shortening the self-initiation delay time. The equivalence ratio, gas temperature, and mass flow rate affect the success ratio of self-initiation. Rotating detonation engine (RDE) can be successfully initiated in the equivalence ratio range of 0.82 to 1.69. Equivalence ratio and gas temperature increase the propagation velocity of rotating detonation wave (RDW), for maximum RDW velocity of 1324.61 m/s, the gas temperature is 1021.3 °C. At the double wave collision point, a new weak RDW appears that decreases the RDE operating stability and a periodic quenching and re-initiation of RDW phenomenon occurs at that point.

Enhanced machine learning—ensemble method for estimation of oil formation volume factor at reservoir conditions

Since the oil formation volume factor (Bo) is crucial for various calculations in petroleum engineering, such as estimating original oil in place, fluid flow in the porous reservoir medium, and production from wells, this parameter is predicted using conventional methods including experimental tests, correlations, Equations of State, and artificial intelligence models. As a substitute to conventional black oil methods, the compositional oil method has been recently used for accurately predicting the oil formation volume factor. Although oil composition is essential for estimating this parameter, it is time-consuming and cost-intensive to obtain through laboratory analysis. Therefore, the input parameter of dissolved gas in oil has been used as a representative of the amount of light components in oil, which is an effective factor in determining oil volume changes, along with other parameters, including pressure, API gravity, and reservoir temperature. This study created machine learning models utilizing Gradient Boosting Decision Tree (GBDT) techniques, which also incorporated Extreme Gradient Boosting (XGBoost), GradientBoosting, and CatBoost. A comparison of the results with recent correlations and machine learning methods adopting a compositional approach by implementing tree-based bagging methods: Extra Trees (ETs), Random Forest (RF), and Decision Trees (DTs), is then performed. Statistical and graphical indicators demonstrate that the XGBoost model outperforms the other models in estimating the Bo parameter across the reservoir pressure region (above and below bubble point pressure); the new method has significantly improved the accuracy of the compositional method, as the average absolute relative deviation is now only 0.2598%, which is four times lower than the previous (compositional approach) error rate. The findings of this study can be used for precise prediction of the volumetric properties of hydrocarbon reservoir fluids without the need for conducting routine laboratory analyses by only employing wellhead data.

Sintering window and sintering mechanism for diamond

High performance sintered diamond tools, such as those applied to wire drawing and rock drilling, represent a considerable advance in hard materials technology. A dense diamond-metal composite is produced using liquid phase sintering. With a cemented carbide substrate, a cobalt-rich liquid infiltrates between the diamond grains at temperatures near 1400 °C. For small diamond particles (nominally below 20 μm), a combination of high pressure (5 GPa or more) and high temperature (1400 °C or more) gives full density in minutes. A sintering window is defined by the pressure and temperature combination that avoids graphitization while ensuring cobalt melt infiltration. The sintering mechanism is carbon transport by dissolution of graphite from low pressure regions away from grain contacts with precipitation of diamond at grain contacts under high pressure. Sinter bonds preferentially nucleate at surface defects, such as screw dislocation spirals. Bonding rates depend on particle size, carbon solubility, temperature, pressure, and hold time. Calculations are shown for interface reaction site limited growth kinetics.

Flow Topology of a Slanted Cylinder with Rounded-Edges Under Compressible Conditions

In this study, the slanted afterbody was modified to more closely represent cargo aircraft afterbodies through the addition of a basal edge fillet. Two slant angles ( and ) were explored over two Mach numbers ( and ) and two Reynolds numbers ( and ) using oil flow visualization and pressure-sensitive paint to identify surface flow phenomena, while the spanwise shadowgraph enabled the observation of mean wake phenomena. The rounded-edge afterbody surface measurements displayed a centerline-separated vortex state with flow features and regions of suction qualitatively similar to those of the baseline sharp-edge case, with some notable differences. For example, a separation bubble at the slant leading edge is nearly twice the size of the baseline sharp-edge model. This is accompanied by the presence of a “source point,” indicated by a region of high pressure where the flow reattaches, and a tighter counter-rotating vortex pair in comparison to the baseline. The rounded-edge prevented the previously seen compressible transition to a fully separated wake state within the Mach number range studied while showing an increase in separation bubble size with increasing Mach number. Also noteworthy was the existence of a new vortex state for the model, where the flow remains attached at the model centerline. This is in contrast to the previously observed flow topology of the centerline-separated vortex state in the sharp-edge model, which formed a separation bubble at the model centerline. The transition between the new centerline-attached vortex state and the traditional centerline-separated vortex state was shown to be dependent on both Mach number and Reynolds number, revealing the importance of boundary-layer development on the rounded afterbody flowfield. Overall, these observations indicate that the rounded afterbody produces flowfields with distinct features that vary from the previously described sharp-edge afterbody wake field under certain conditions.

Tests for Validation Problems of Anomalous Separated Flow and Heat Transfer Enhancement on Structured Surfaces with Extraordinary Pressure Drops

New tests are presented for application packages and turbulence models for validation problems of high-intensity vortex flows near structured energy-efficient surfaces. The idea of testing is based on the discovery of anomalous intensification of separated flows and heat transfer in inclined grooves on plates and channel walls. In the grooves, due to the extraordinary pressure drops, confirmed by experiments, swirling flows are generated with high velocities of the return and secondary flow, comparable to the speed of the external flow. Also, high-gradient zones with friction and heat transfer are formed inside the grooves, many times (from 1.5–2 to 7–9 times) exceeding friction and heat transfer on a flat wall. As an example, the VP2/3 package, developed on the basis of original multi-block computing technologies and using multi-scale intersecting grids, is being tested. Comparison of numerical predictions with Zubin’s experiments confirmed high static pressure drops between the stagnation zone on the windward slope of the inclined groove and the negative pressure region at the site of generation of a tornado-like flow on the inlet spherical segment, and also demonstrated the acceptability of the RANS approach for predicting the characteristics of high-intensity swirling flows.

ТЕРМОДИНАМИЧЕСКИЙ АНАЛИЗ ПРОЦЕССА ФОРМИРОВАНИЯ НАНОСТРУКТУРНОГО ПОЛИКРИСТАЛЛИЧЕСКОГО МАТЕРИАЛА НА ОСНОВЕ НАНОАЛМАЗОВ, МОДИФИЦИРОВАННЫХ НЕАЛМАЗНЫМ УГЛЕРОДОМ (ЧАСТЬ 1)

The influence of the size of carbon particles on the parameters of the graphite–diamond phase transformation is considered. It is shown that the surface energy of carbon nanoparticles of various shapes (spherical, columnar) makes a significant contribution to their total thermodynamic potential, which leads to a shift in the diamond–graphite equilibrium curve to the low pressure region and an expansion of the diamond phase stability region. At the same time, the change in the chemical potential (Gibbs free energy) during the direct (not catalytic) transition of thin-film graphite-like nanostructures into diamond will be higher than for “massive” graphite, which leads to an increase in the pressure of phase transformation into diamond. To reduce the parameters of diamond formation and obtain nanostructured diamond polycrystals, it is proposed to use nanodiamond particles with a nanometer surface layer of non-diamond (graphitelike) carbon as the starting material. In this case, the nanodiamond surface will influence the transition of a nanometer layer of graphite (graphite-like carbon) into diamond under more favorable thermodynamic parameters.

Radiative heat transfer on the peristaltic flow of an electrically conducting nanofluid through wavy walls of a tapered channel

Present analysis deals with the characteristics of radiative heat on the peristaltic flow of nanofluid through wavy walls of a tapered channel. Peristaltic flows within the pumping process arise in the region having lower to higher pressure region. Assumption of velocity slip along with the convective boundary condition energizes the thermal system as well as the flow phenomena. However, the combined effect of Brownian motion and thermophorsis due to the cross-diffusion effect affects the flow properties. One of the significant applications of the flow is that the blood pumping in the human body. It acts as a vehicle through the liquid that past through the wavy channels walls contacting liquids expands in its length due to the dynamical rush. However, solution of the transformed governing flow phenomena is obtained by employing approximate analytical technique known as Variation Parameter Method (VPM). The characteristics of the parameters involved in the system are presented via graphs. Present outcome warrants that, the significance of magnetic strength and flow through the permeable medium may favours to enhance the pumping procedure as the pressure gradient lower down in the non-Darcy medium found to be one of the important observations. Further, significant enhancement in the fluid temperature and concentration profile is exhibited due to the consideration of the convective conditions i.e. the augmentation in the thermal and solutalBiot numbers respectively.