Kinetic Energy Of Fluid Research Articles

Mixed convective thermal transport in a lid-driven square enclosure with square obstacle

The prime motive of this disquisition is to scrutinize simultaneous aspects of external forcing mechanism and internal volumetric forces on non-Newtonian liquid filled in square enclosure. Inertially driven upper lid is assumed by providing constant magnitude of slip velocity whereas thermal equilibrium is disturbed by assuming uniform temperature at lower boundary and by keeping rest of walls as cold. To enhance thermal diffusion transport with in the flow domain cold as well as adiabatic temperature situation is provided. In view of velocity constraints all the extremities at no-slip except the upper wall which is moving with ULid. Formulation is attained in dimensional form initially and afterwards variables are used to convert constructed differential system into dimensionless representation. A numerical solution of leading formulation is sought through Galerkin finite element discretization. Momentum and temperature equations are interpolated by quadratic polynomials whereas pressure distribution is approximated by linear interpolating function. Domain discretized version is evaluated in view of triangular and rectangular elements. Newton’s scheme is employed to resolve the non-linearly discretized system and a matrix factorization based non-linear solver renowned as PARADISO is used. Validation of results is ascertained by forming agreement with existing studies. In addition, grid independence test is also performed to show credibility of performed computations. Stream lines and isothermal contours patterns are portrayed to evaluate variation in flow distributions. Kinetic energy and local heat flux for uniform and non-uniform heating situations are also divulged in graphical and tabular formats. Increase in Reynold number produces decrease in kinetic energy of fluid. Enhancement in Grashof number causes enrichment of thermal buoyancy forces due to which Nusselt number uplifts. Clock wise rotations increase against upsurge in magnitude of Reynold number which is evidenced form stream lines. Squeezing of secondary vortex against Prandtl number arises due to dominance of viscous forces.

Hydro- and thermo-dynamic characteristics of a circular cylinder placed in mixed convection flow

The fluid–thermal–structure interaction of a heated circular cylinder is numerically investigated at Pr = 0.71, Re = 60–160, and Ri = 0–2.0 in this article using the stabilized finite element method. The heat convection characteristics along the cylinder's surface in both forced and mixed convection subject to cross buoyancy are discussed and linked to the fluid instabilities. Additionally, the hydrodynamic characteristics are investigated in both time and frequency domains according to the strength of thermal cross buoyancy. Multiple harmonics of hydrodynamic coefficients and heat convection are identified from their frequency domains. Reynolds stresses are utilized to study the energy cascade of fluid kinetic energy and thermal energy via the fine-scale fluid fluctuation in the wake. Furthermore, the dynamic mode decomposition (DMD) technique is employed to extract the dominant spatial-temporal modes from the original field data. It is found that more linear DMD modes are required to accurately reconstruct the vorticity and temperature contours. It implies that strong nonlinear features exist in the wake and are influenced by the thermal buoyancy.

Grain-resolving simulations of submerged cohesive granular collapse

We investigate the submerged collapse of weakly polydisperse, loosely packed cohesive granular columns, as a function of aspect ratio and cohesive force strength, via grain-resolving direct numerical simulations. The cohesive forces act to prevent the detachment of individual particles from the main body of the collapsing column, reduce its front velocity, and yield a shorter and thicker final deposit. All of these effects can be captured accurately across a broad range of parameters by piecewise power-law relationships. The cohesive forces reduce significantly the amount of available potential energy released by the particles. For shallow columns, the particle and fluid kinetic energy decreases for stronger cohesion. For tall columns, on the other hand, moderate cohesive forces increase the maximum particle kinetic energy, since they accelerate the initial free-fall of the upper column section. Only for larger cohesive forces does the peak kinetic energy of the particles decrease. Computational particle tracking indicates that the cohesive forces reduce the mixing of particles within the collapsing column, and it identifies the regions of origin of those particles that travel the farthest. The simulations demonstrate that cohesion promotes aggregation and the formation of aggregates. Furthermore, they provide complete information on the temporally and spatially evolving network of cohesive and direct contact force bonds. While the normal contact forces are aligned primarily in the vertical direction, the cohesive bonds adjust their preferred spatial orientation throughout the collapse. They result in a net macroscopic stress that counteracts deformation and slows the spreading of the advancing particle front.

Molecular kinetic modelling of nanoscale slip flow using a continuum approach

One major challenge for a continuum model to describe nanoscale confined fluid flows is the lack of a boundary condition that can capture molecular-scale slip behaviours. In this work, we propose a molecular-kinetic boundary condition to model the fluid–surface and fluid–fluid molecular interactions using the Lennard–Jones type potentials, and add a mean-field force to the momentum equation. This new boundary condition is then applied to investigate the nanoscale Couette and Poiseuille flows using the generalised hydrodynamic model developed by Guo et al. (Phys. Fluids, volume 18, issue 6, 2006a, 067107). The accuracy of our model is validated by molecular dynamics simulations and other models for a broad range of parameters including density, shear rate, wettability and channel width. Our simulation results reveal some unexpected and unintuitive slip behaviours at the nanoscale, including the epitaxial layering structure of fluids and the slip length minimum. The slip length minimum, which is analogous to the Knudsen minimum, can be explained by competing fluid–solid and fluid–fluid molecular interactions as density varies. A new scaling law is proposed for the slip length to account for not only the competing effect between the fluid–solid and fluid–fluid molecular interactions, but also many other physical mechanisms including the competition between the fluid internal potential energy and kinetic energy, and the confinement effect. While the slip length is nearly constant at the low shear rates, it increases rapidly at the high shear rates due to friction reduction. These molecular-scale slip behaviours are caused by energy corrugations at the fluid–solid interface where strong fluid–solid and fluid–fluid molecular interactions interplay.

On-Chip Arbitrary Manipulation of Single Particles by Acoustic Resonator Array.

Effective and arbitrary manipulation of particles in liquid has attracted substantial interest. Acoustic tweezers, a new and promising tool, exhibit high biocompatibility, universality, and precision but lack arbitrariness. In this work, we report a gigahertz (GHz) bulk acoustic streaming tweezer (AST)-based micro-manipulation platform capable of efficiently translating acoustic energy to fluid kinetic energy, creating a controllable, quick-response, and stable flow field and precisely, arbitrarily, and universally manipulating a single particle to move like a microrobot. Through controlling the radio frequency signals applied on these resonators, the intensity and direction of the acoustic streaming flow can be quickly and arbitrarily adjusted. Consequently, the particle dispersed at the bottom can be arbitrarily and steadily driven along the predesigned route to the target position by the acoustic streaming drag force (ASF). We utilized four resonators cooperated as a work group to manipulate single SiO2 particles to complete nearly uniform linear motions and U-shaped motions, as well as playing billiards and exploring a maze, demonstrating the enormous potential of this GHz AST-based single-particle manipulation platform for separation, assembly, sensing, enriching, transporting, and so forth.

The CFD Application in Analyzing The 024P108 Centrifugal Pump Damage as The Effect of High Vibration using Fluid Flow Discharge Capacity Parameters

Petroleum is one of the natural resources that can produce energy both for fuel and for generating electricity. One of the most important and widely used equipment in this industry is a pump. A pump is a device for distributing fluids from one place to another. A centrifugal pump is a device for distributing move liquids from one place to another by converting the fluid's kinetic energy into potential energy through an impeller that rotates in the housing. The objective of this research is to analyze the damage of pump 024P108, which indicated high vibration due to using a high-speed shaft. The research is done by using an analytical method, using CFD Fluent analysis with flow discharge capacity under normal conditions and minimum flow conditions, and comparing the results by API 610. Afterward, the right maintenance will be known for the 024P108 centrifugal pump to reduce the high vibration that occurred in the pump. The pump is run at minimum flow with a flow rate of 22 m3/hr and the normal flow rate of the pump is 97.9 m3/hr so that the results show that the pump head has decreased to 198.74 m and the pressure drop has increased by 2.5995×105 Pa. The vibration test data shows that high vibration of 8.5 mm/s is produced by a minimum flow state of 22 m3/hr, this low fluid flow is the cause of high vibration on the pump. High vibration has an impact on pump performance, that is decreasing pump performance (efficiency) and if left continuously it can cause damage to the pump.

Experimental Analysis of Flow Characteristics and Annular Flow Boundaries of the Highly Viscous Oil/Water Lubricated Flow

Summary Theoretical research on the characteristics of two-phase flow in horizontal pipelines is very important in the petroleum industry because a large amount of pumping power can be derived from the water-lubricated transportation of heavy or extraheavy crude oil. Experimental research of oil/water two-phase flow with water as the continuous phase in horizontal pipelines is carried out using tap water and two mineral oils with viscosity of approximately 0.743, 412, and 686 mPa·s, respectively. Two oil/water mixing devices of a water-ring generator and T-shaped three-way pipe are adopted to compare the effect of oil/water annular flow. Pressure drop parameters, apparent viscosity, clear pictures, flow pattern maps, and resistance characteristics of oil/water two-phase flow are displayed in this article, together with comprehensive comments. Moreover, obtained results are compared with theoretical findings, experimental results, and empirical laws of different scholars in the literature. According to the ratio of fluid kinetic energy (inertial force) to potential energy (buoyancy), Froude number (Fr) is introduced to reach the state of hydrodynamic lift balance. Based only on experimental observations of the position of the layered/annular transition, a novel criterion is proposed to determine the regions with suitable operating conditions for application.

Making Better Swirl Brakes Using Computational Fluid Dynamics: Performance Enhancement From Geometry Variation

Abstract A fluid with a large swirl (circumferential) velocity entering an annular pressure seal influences the seal cross-coupled dynamic stiffness coefficients, and hence it affects system stability. Typically comprising a large number of angled vanes around the seal circumference, a swirl brake (SB) is a mechanical element installed to reduce (even reverse) the swirl velocity entering an annular seal. SB design guidelines are not readily available, and existing configurations appear to reproduce a single source. By using a computational fluid dynamics (CFD) model, the paper details a process to engineer a SB upstream of a 16-tooth labyrinth seal (LS) with tip clearance Cr = 0.203 mm. The process begins with a known nominal SB* geometry and considers variations in vane length (LV* = 3.25 mm) and width (WV* = 1.02 mm), and stagger angle (θ* = 0 deg). The vane number NV* = 72 and vane height HV* = 2.01 mm remain unchanged. The SB–LS operates with air supplied at pressure PS = 70 bar, a pressure ratio PR = exit pressure Pa/PS = 0.5, and rotor speed Ω = 10.2 krpm (surface speed ΩR = 61 m/s). Just before the SB, the preswirl velocity ratio = average circumferential velocity U/shaft surface speed (ΩR) equals α = 0.5. For the given conditions, an increase in LV allows more space for the development of vortexes between two adjacent vanes. These are significant to the dissipation of fluid kinetic energy and thus control the reduction of α. A 42% increase in vane length (LV = 4.6 mm) produces a ∼43% drop in swirl ratio at the entrance of the LS (exit of the SB), from αE = 0.23 to 0.13. Based on the SB with LV = 4.6 mm, the stagger angle θ varies from 0 deg to 50 deg. The growth in angle amplifies a vortex at ∼70% of the vane height, while it weakens a vortex at 30% of HV. For θ = 40 deg, the influence of the two vortexes on the flow produces the smallest swirl ratio at the LS entrance, αE = −0.03. For a SB with LV = 4.6 mm and θ = 40 deg, the vane width WV varies from 0.51 mm to 1.52 mm (±50% of WV*). A reduction in WV provides more space for the strengthening of the vortex between adjacent vanes. Therefore, a SB with greater spacing of vanes also reduces the inlet circumferential velocity. For WV = 0.51 mm, αE further decreases to −0.07. Besides the design condition (α = 0.5), the engineered SB having LV = 4.6 mm, θ = 40 deg, and WV = 0.51 mm effectively reduces the circumferential velocity at the LS entrance for other inlet preswirl ratios equaling α = 0 and 1.3. Rather than relying on extensive experiments, the CFD analysis proves effective to quickly engineer a best SB configuration from the quantification of performance while varying the SB geometry and inlet swirl condition.

Enlarged Lumen Volume of Proximal Aortic Segment and Acute Type B Aortic Dissection: A Computer Fluid Dynamics Study of Ideal Aortic Models.

BackgroundRecent study has revealed that enlarged diameters of the ascending aorta and proximal aortic arch enhance the probability of ATBAD. However, little is understood about the relation to ATBAD.ObjectiveThis study explored the differences in proximal aortic segment (PAS) morphology in patients with acute type B aortic dissection (ATBAD), and performed hemodynamic simulations to provide proof of principle.Materials and MethodsThe morphological characteristics of PAS in the ATBAD group (n = 163) and corresponding segment in the control group (n = 120) were retrospectively measured. The morphological parameters were analyzed using comprehensive statistical approaches. Ridge regression analysis was also performed to determine the association between independent variable and dependent variable. P < 0.01 was considered significant. Idealized aortic models were established based on variables of statistical significance, and hemodynamic simulations were performed to evaluate blood flow changes caused by morphology.ResultsDiameters at landmarks of PAS were significantly larger in the ATBAD group. The lumen volume (VPAS) of PAS in the ATBAD group was significantly enlarged than that of the control group (124,659.07 ± 34,089.27 mm3 vs 89,796.65 ± 30,334.40 mm3; P < 0.001). Furthermore, the VPAS was positively correlated to diameters. As the VPAS increased, the fluid kinetic energy in PAS enhanced linearly, and time-averaged wall shear stress and oscillatory shear index at the distal area of the left subclavian artery increased significantly.ConclusionIn the ATBAD group, the enlarged VPAS and increased diameters of PAS are positively correlated. Meanwhile, the enlarged VPAS leads to more aggressive hemodynamic parameters at the distal area of the left subclavian artery, which may create a contributory condition for ATBAD.

Conversion of Fluid Kinetic and Pressure Energy in Compression Process of a Gas Turbine: Thermodynamic Analysis and Cfd Validations

Conversion of Fluid Kinetic and Pressure Energy in Compression Process of a Gas Turbine: Thermodynamic Analysis and Cfd Validations

Numerical investigation on flow induced vibration performance of flow-around structures with different angles of attack

The concept of energy harvesting based on flow-induced vibration (FIV) used in a new application field of long-distance transport pipelines is proposed in this paper, the fluid kinetic energy in pipelines is harvested and converted into electricity, to provide uninterrupted power for sensors along pipelines, realizing remote monitoring and management of pipelines at lower cost. This paper aims to find the shape features of flow-around structure that enhance FIV and harvest energy more effectively, giving design references for the geometrical shape of energy harvester. To independently study the influence of vortex shedding position on the FIV performance, the FIV responses, wake patterns and energy conversion efficiency of structures with different angles of attack that have different vortex shedding positions are numerically studied versus frequency ratios in this paper. Results show that the more forward vortex shedding position determines the higher FIV response, and the criterion for the shape feature of structure on its upstream side that enhance FIV is summarized. Results also show the energy conversion efficiency is the result of FIV amplitude, oscillating frequency and fluid force, which isn't completely positively correlated with FIV amplitude. Each structure obtains the maximum energy conversion efficiency at frequency ratio of 0.7.

A machine-learning approach to predicting the energy conversion performance of centrifugal pump impeller influenced by blade profile

Centrifugal pump is a kind of energy conversion machine for fluid delivering. It transfers the mechanical energy of impeller to the potential and kinetic energy of fluid. As a key factor in influencing the energy conversion performance of centrifugal pump, blade profile design is crucial. Traditional design concepts have ideal assumptions. To have a better design guidance, machine-learning based on neural network is used in this study. A typical centrifugal pump with simplified blade profile is numerically studied with experimental validation for a better discussion. Statistical results show that, for the high dimensional nonlinear relationship between blade angle and performance of centrifugal pump, neural network can adapt to this complex correlation better. The blade installation angle at leading-edge ( βLE′) and trailing-edge ( βTE′) and the wrap angle (Δ θ′) has significant correlation with the performance including pump head H, pump efficiency η, impeller head Himp, impeller efficiency ηimp and volute loss Δ Hvol. The influence level of blade angle follows the high-to-low order of Δ θ′, βLE′ and βTE′. Determination of blade profile can be done for improving the energy conversion efficiency. Optimal blade profiles have higher βLE′ and Δ θ′ with better flow-control ability. Compared with the blade parameters of the initial pump, the blade profile with the best centrifugal pump efficiency is the best βLE′ increased by 1.926°, Δ θ′ increased by 9.858°, Optimization of impeller efficiency βLE′ increased by 1.855°, Δ θ′ increased by 9.421°. Computational fluid dynamics indicate the elimination of vortex in impeller after optimal selection. Then, βTE′ and Δ θ′ are found influential in aggravating the circumferential flow component in this special circular-volute with generating higher loss. βTE′ has a positive correlation with impeller head which suits traditional theory. In general, the machine-learning using neural network is effective in determining blade profiles for enhancing the performance of centrifugal pump.

Coordinated layout planning of ocean current turbines and collector system considering spatial velocity distribution

Ocean current generation has become a popular form of supplying electric energy by using fluid kinetic energy. For ocean current, the key difference from other planning can be embodied in the turbine layout planning region, which needs to be considered as a three-dimensional area. Considering that, this paper investigates the three-dimensional ocean current turbines and collector system coordinated layout planning model. First, a velocity-depth curve of interest current area is determined by fitting historical velocity data. Then, a three-dimensional ocean current wake model is derived through the integral form of momentum conservation to analyze the influence of the wake effect on the velocity of the three-dimensional distributed turbine array. Finally, a two-level three-dimensional location and capacity planning model is established which involve three-dimensional topology constraints, with the upper-level goal of minimizing the whole system cost, and the lower-level goal of minimizing the cost of power collection topology. The accuracy and effectiveness of the proposed model are investigated through the case study on the current data of the Gulf of Mexico.

Structural subgrid scale model based on wavelet filter for large eddy simulation of particle-laden turbulence

Coherent vortex structures in subgrid scale (SGS) motions are important for preferential concentration and collision of particles with small and intermediate Stokes number (Xiong et al., 2019). In this study, a new large eddy simulation (LES) strategy that combines wavelet filtered large eddy simulation with a differential filter SGS model is proposed. First, a wavelet filtered direct numerical simulation (WFDNS) enables good preservation of SGS structures due to the high compressibility and local fidelity of the wavelet filter. Second, a differential filter (DF) model, containing only a parameter related to the nominal filter width, is used to dynamically reconstruct unresolved eddies. The SGS model presented here is verified using direct numerical simulation (DNS) data for particle-laden homogenous isotropic turbulence. Compared to the classical spectral-filtered DNS (FDNS) model, the new SGS model enables to achieve better agreement with DNS results related to the dispersed-phase statistics, such as particle acceleration, particle-seen fluid kinetic energy, particle-seen Lagrangian integral time etc. Furthermore, obtained results also exhibit the advantages of a proposed model over the stochastic Langevin model in the prediction of particle dynamics, especially collision-related statistics such as radial distribution function, radial relative velocities, and particle collision rates. Moreover, the model also demonstrates good performance in application to particle-pair related statistics at different Reynolds numbers and different filter depths. This is attributed to the ability of this model to multispectrally enhance coherent vortex structures in SGS, which is promising to apply for recovering SGS effects in the LES of turbulent particle-laden flows.

Numerical study of the magnetohydrodynamic flow instability and its effect on energy conversion in the annular linear induction pump

A numerical model of annular linear induction pump with a full-scale pump channel is created to study the scale-dependent instability of the magnetohydrodynamic flow. The magnetic-fluid coupling effect is implemented by modifying the underlying governing equations and constraints. The model authenticity is validated by comparing the simulated pressure difference, as well as the pressure pulsation, with the previous experimental data. The flow patterns at different flow rates corresponding to different magnetic Reynolds numbers are depicted from both the azimuthal and meridian viewpoints, and the periodicity of the occurring vortex flows is found in the pump. By analyzing the different mechanisms contributing to the fluid kinetic energy, it is found the competition between the axial components of the Lorentz force and pressure gradient dominates the flow evolution in the pump channel. The magnetic-fluid coupling effect is found to amplify the disturbances in either the magnetic field or the fluid field. It is even effective within the uniform externally imposed magnetic field and inlet velocity only if a disturbance exists in the initial flow. Increase in the cycle number of disturbance can enhance the flow stability and induce smaller vortex flows. Finally, different mechanisms of energy conversion in the pump are analyzed and it is found that the sudden occurrence of vortex flows can induce large current density, which significantly increases the Ohmic dissipation and decreases the efficiency of energy conversion from magnetic field into the fluid. The relatively large Ohmic dissipation in the fluid is the main reason for the low efficiency of such a device.

Modelling flow for finite conductivity in long horizontal oil wells

The impact of neglected well bore pressure losses due to fluid accumulation and kinetic energy in the fundamental energy equation used for derivation of flowing bottom-hole pressure in horizontal well have been conceived to be a considerable reason for the discrepancy between computed rates from the existing models and actual rates got from production tests. In the study, a new model that investigate all possible well bore pressure losses effect on the production rate of a horizontal oil well have been established. The newly developed model has been validated using the field data obtained from the literature and outcome got from the new model yields more satisfactory results. A more realistic results that evident all flow phenomena in petroleum production well include the initial unsteady, pseudo-steady and steady state flow condition hence flow rate at any given production time has been established for flow of oil along horizontal production well. The concept is useful to estimate flowing bottom-hole pressure and analyze its effect on production rate value of a horizontal oil well without ignoring any pressure resisting terms in the governing thermodynamic equation. The unsteadiness fluid flow period that generally observed after shut in a well have also been demonstrated. Closer agreement between the results obtained using the newly developed model and real life field measurement was observed when compared with the previous model in the literature. The study gives reservoir engineer an exact and helpful device for estimating and assessing horizontal oil well production rate.

A hybrid simulation of gravitational wave production in first-order phase transitions

The LISA telescope will provide the first opportunity to probe the scenario of a first-order phase transition happening close to the electroweak scale. In thermal transitions, the main contribution to the GW spectrum comes from the sound waves propagating through the plasma. Current estimates of the GW spectrum are based on numerical simulations of a scalar field interacting with the plasma or on analytical approximations — the so-called sound shell model. In this work we present a novel setup to calculate the GW spectra from sound waves. We use a hybrid method that uses a 1d simulation (with spherical symmetry) to evolve the velocity and enthalpy profiles of a single bubble after collision and embed it in a 3d realization of multiple bubble collisions, assuming linear superposition of the velocity and enthalpy. The main advantage of our method compared to 3d hydrodynamic simulations is that it does not require to resolve the scale of bubble wall thickness. This makes our simulations more economical and the only two relevant physical length scales that enter are the bubble size and the fluid shell thickness (that are in turn enclosed by the box size and the grid spacing). The reduced costs allow for extensive parameter studies and we provide a parametrization of the final GW spectrum as a function of the wall velocity and the fluid kinetic energy.

Static and Rotordynamic Characteristics for Two Types of Novel Mixed Liquid Damper Seals With Hole-Pattern/Pocket-Textured Stator and Helically Grooved Rotor

Abstract Noncontacting liquid annular seals, such as helical groove seals, are widely used at the impeller interstage and shaft end in the liquid turbomachinery to reduce the fluid leakage and stabilize the rotor-bearing system. However, previous literatures have expounded that the helical groove seal possesses the poor sealing property at low rotational speed condition and suffers the rotor instability problem inducing by negative stiffness and damping, which is undesirable for the liquid turbomachinery. In this paper, to obtain the high sealing performance and the reliable rotordynamic capability throughout full operational conditions of machines, two novel mixed liquid damper seals, which possess a hole-pattern/pocket-textured stator matching with a helically grooved rotor, were designed and assessed for the balance piston location in a multiple-stage high-pressure centrifugal liquid pump. To assess the static and rotordynamic characteristics of these two types of mixed liquid damper seals, a three-dimensional (3D) steady computational fluid dynamics (CFD)-based method with the multiple reference frame theory was used to predict the seal leakage and drag power loss. Moreover, a novel 3D transient CFD-based perturbation method, based on the multifrequency one-dimensional stator whirling model, the multiple reference frame theory, and the mesh deformation technique, was proposed for the predictions of liquid seal rotordynamic characteristics. The reliability and accuracy of the present numerical methods were demonstrated based on the published experiment data of leakage and rotordynamic force coefficients of a helical groove liquid annular seal and a hole-pattern liquid annular seal. The leakage and rotordynamic force coefficients of these two mixed liquid damper seals were presented at five rotational speeds (0.5 krpm, 2.0 krpm, 4.0 krpm, 6.0 krpm, and 8.0 kpm) with large pressure drop of 25 MPa, and compared with three types of conventional helical groove seals (helical grooves on rotor, stator or both), two typical damper seals (hole-pattern seal, pocket damper seal with smooth rotor), and a mixed helical groove seal. Numerical results show that two novel mixed liquid damper seals both possess generally better sealing capacity than the conventional helical groove seals, especially at lower rotational speeds. The circumferentially isolated cavities (hole/pocket types) on the stator can enhance the “pumping effect” of the helical grooves for mixed helical groove seals, by weakening the swirl flow in seal clearance (which results in the increase of the fluid velocity gradient near the helically grooved rotor). What is more, the helical grooves on rotor also strengthen the dissipation of fluid kinetic energy in the isolated cavities, so the mixed liquid damper seals offer less leakage. Although the mixed liquid damper seals possess a slightly larger (less than 40%) drag power loss, it is acceptable in consideration of the reduced (∼60%) leakage for the high-power turbomachinery, such as the multiple-stage high-pressure centrifugal liquid pump. The present novel mixed liquid damper seals have pronounced rotordynamic stability advantages over the conventional helical groove seals, due to the obviously larger positive stiffness and damping. The mixed liquid damper seal with the hole-pattern stator and the helically grooved rotor (HPS/GR) possesses the lowest leakage and the largest effective damping, especially for higher rotational speeds. From the viewpoint of sealing capacity and rotor stability, the present two novel mixed liquid damper seals have the potential to become the attractive alternative seal designs for the future liquid turbomachinery.

Overall Scheme of the Pipes Robot for Charging Using Fluid Kinetic Energy

According to the design requirements of the pipeline robot and the influence of the surrounding environment on the robot, in this paper, the overall structure of the robot is designed. Including the shape of the robot, the wall thick, structure. The stepping motor is used to drive the driving wheel to roll to realize the robot’s walking; the oil dirt on the pipe wall is cleaned by steel brush; the internal and external pressure balance method of the body is used for the sealing of the robot.

Design optimization of hydrodynamic coupling applying response surface method combined with CFD technique

Hydrodynamic coupling is a type of fluid machinery that uses fluid kinetic energy to transmit power. In this paper, meridional profile optimization of fully filled fluid coupling was performed to improve transmitted torque. The response surface method, a global optimization method, combined with CFD was introduced to find optimum meridional profile of blades. The torque coefficient was applied as an objective function. The response surface method was adopted with three design variables: hydraulic diameter ratio of blades, central core position, and meridional profile of the hub. Results showed that the best diameter ratio occurred at d/D =0.67. To specify an optimal position for the central core, a dimensionless parameter (b/d) was introduced. With regression analysis, it was found that the optimal point occurs at about b/d =0.37. It was confirmed with the results of contour and vector plots. Three types of curves (circular, elliptical, and cubic Bezier curve) were employed to optimize the meridional shape of blades. The circular curve was applied in the design of the hub in the reference geometry. Relative to the circular curve hub, the use of elliptic curve had no significant effect on the objective function. Two dimensionless parameters, l1/d and l2/d, were defined to investigate the effect of Bezier curves on the performance of hydrodynamic coupling. The optimum values for design variables of l1/d and l2/d were obtained 0.80 and 0.88, respectively.