Prediction Of Pressure Loss Research Articles

Predicting pressure loss of turbulent non-Newtonian fluids in annuli under temperature and pipe rotation effects using optimization algorithms

Accurate estimation of frictional pressure loss in an annulus is crucial for selecting appropriate pump systems, determining horsepower requirements, and controlling hole cleaning. Generally, when calculating the friction factor, the temperature of the fluid and the rotation of the inner pipe are not considered, which can lead to errors in estimating the pressure difference in the annulus. In this study, to ensure accurate pressure drop calculations, the effects of temperature and inner pipe rotation, along with other parameters, were included. An extensive experimental study was conducted at Izmir Katip Celebi University’s Flow Loop using two Carboxymethyl cellulose (CMC) solutions, across various fluid velocities, fluid temperatures, diameter ratios, and inner pipe rotation speeds. A dimensional analysis was performed to identify the parameters that affect friction factors in the annulus. Finally, friction factor equations were developed based on the experimental data using optimization algorithms such as interior point (fmincon), genetic, minimax, and simulated annealing. The findings showed that the predictions from all the algorithms tested in the study closely matched the experimental results; however, the interior point algorithm (fmincon) provided the best performance, with an average absolute percentage error of 9.4%.

Investigation of the transportation characteristics of marine dredged-sediment in pipelines based on experimental pipeline models

Marine dredged-sediment(DS) is often transported through pipelines, where factors such as the solid volume concentration and transport rate can significantly influence the efficiency of the process. Inadequate selection of transport rates for a given solid volume concentration can lead to substantial energy losses. The pressure loss Δ P L or pressure loss gradient Δ P L / L are critical parameters for assessing energy loss during pipeline transport. In this study, large-scale indoor experiments on DS pipeline transport were conducted to investigate the effects of the cross-sectional mean flow velocity Vavg and solid concentration ϕ on the transport characteristics of DS. The results show that at higher solid volume concentrations, Δ P L / L increases rapidly with the square of Vavg and then plateaus, followed by a linear growth phase. In addition, a linear relationship is observed between lgf and lgVavg when the flow velocity is below critical velocity (Vavg ) critical ; above (Vavg ) critical , the friction factor f stabilizes at f 0 . Formulas for calculating (Vavg ) critical , f 0 and ϕ were developed. Additionally, a method for determining the optimal transport velocity of DS at varying volume concentrations was established, enabling the identification of the most efficient flow velocity for DS pipeline transportation across different concentrations. HIGHLIGHTS Pipeline model tests were conducted on marine dredged sediments. A formula for predicting pressure loss on the basis of solid concentration was derived. The impact of the solid concentration on the Darcy friction factor was determined. A method for determining the optimal transport velocity was established.

Flow regime transition maps and pressure loss prediction of gas, oil and water three-phase flow in the vertical riser downstream 90° bend using data driven approach

The simultaneous flow of gas, oil & water is frequently encountered in pipelines during upstream petroleum operations. The multiphase flow results in different types of flow patterns based on the flow rates of fluids, physical properties and geometry of the flow domain. The flow behavior is characterized based on the governing flow patterns. Hence, the information about the flow patterns, regime maps and resulting pressure loss are important for multiphase flow system design and optimization. The current work is focused on construction of gas, oil and water, three-phase flow regime maps and developing pressure loss prediction correlations for the flow through vertical riser downstream 90° bend. The pipe internal diameter (ID) is 6 inch and the bending radius to pipe diameter ratio is 1. The observed gas-liquid flow patterns are slug, churn, and semi-annular churn flow at the given range of superficial velocities of fluids. The flow pattern data has been used to construct flow regime maps to analyze the variation in flow patterns with flow rates of fluids and compared with the available works in the literature. In addition, the change in pressure loss with respect to flow patterns has been analyzed. Previous models are used for the prediction of pressure loss. However, according to the assessment, the models underpredicted the pressure loss. Based on three-phase pressure loss data, multiple linear regression analysis has been carried out to propose new correlations for pressure loss prediction. Comparison of the calculated and experimental data showed good agreement between the results. The knowledge of flow regime variation and pressure loss correlations can help flow assurance engineers in designing and optimization of multiphase flow systems.

The effect of including dynamic imaging derived airway wall motion in CFD simulations of respiratory airflow in patients with OSA

Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA.

Predictive method of pressure loss in wet clutch caused by seal wear based on stacking ensemble learning

The harsh operating conditions of heavy-duty vehicles accelerates the wear of the sealing ring in the transmission, leading to increased oil leakage and a reduction of the operating pressure in the piston cylinder of wet clutch. This impairs the proper functioning of the transmission in the heavy-duty vehicle. Therefore, it is necessary to predict the pressure loss inside the transmission quickly and effectively after the wear of the sealing ring. The wear of the sealing ring under different operating conditions is calculated through the modified Archard model. The relationship between the oil leakage and pressure loss after the wear of the sealing ring is analyzed using Fluent software. The analysis involves the effects of different wear levels of the sealing ring. The simulation results are validated through a high-speed oil cylinder performance test rig. Based on the validated simulation data and test data, a prediction model for pressure loss is established by using stacking ensemble learning with MLR (multiple linear regression), DTR (decision tree regression), and SVR (support vector regression) as the base learners and RF (random forest) as the meta-learner. The risk of model overfitting is reduced through k-fold cross-validation. The research results indicate that the fused stacking ensemble learning algorithm fully utilizes the advantages of each base learner and can effectively predict the pressure loss after the wear of the sealing ring, and achieve a higher accuracy. The establishment of this model provides theoretical support for real-time prediction of pressure loss after the wear of the sealing ring in actual heavy-duty vehicles.

Ammonia single-phase and two-phase frictional pressure losses in horizontal smooth and straight inner-grooved tubes

The experimental study of single-phase and two-phase frictional pressure losses has been performed with ammonia flow in stainless steel smooth tubes (internal diameter of 5.5 mm and 8.5 mm) and six straight inner-grooved aluminium tubes with different nominal diameters (7.15 to 13.3 mm), length (0.45 to 2.0 mm) and thickness (0.35 to 0.8) of fins. Single-phase test boundary conditions correspond to Reynolds numbers of 1000 to 20,000. Two-phase tests have been carried out at saturation temperature of 45 to 65 °C, mass velocity of 50 to 210 kg·m−2s−1 and vapour quality of 0.1 to 0.9. Comparison of obtained test data with the existing frictional losses approaches shows that the Blasius model is appropriate to single-phase flows in smooth tubes, and Müller-Steinhagen and Heck's (1986) model is most accurate in predictions of two-phase frictional losses in smooth tubes. Existing approaches of single-phase frictional pressure loss predictions in the pipes and channels with longitudinal fins (Carnavos, 1980; Edwards and Jensen, 1994) are not adequately suited to the ammonia test points obtained in the considered straight inner-grooved tubes. A new semi-empirical model has been proposed, based on generalisation around the revealed geometric dimensionless factor, which accurately describes friction pressure losses in the considered inner-finned profiles. The simplest homogeneous model for defining two-phase friction pressure losses, using McAdams et al.'s (1942) recommendation for mixture dynamic viscosity definition and a new model of single-phase friction factor, best fit both quantitatively and qualitatively to ammonia two-phase test points in most of the considered straight inner-grooved tubes.

Roughness Related to Cooling Performance of Channels Made Through Additive Manufacturing

Abstract The complex surface morphology and multiscale surface features inherent in additively manufactured (AM) components contribute to the overall flow characteristics and heat transfer of cooling passages. As the AM process and cooling data in the literature continue to evolve, so does the need for more accurate heat transfer and pressure loss correlations for AM cooling schemes. This study improves the predictability of pressure loss and heat transfer for AM cooling passages by fabricating a range of coupons and investigating samples in the literature. Twenty-seven test coupons were manufactured using direct metal laser sintering in an assortment of build directions and build locations that produced a variety of surface morphologies. Nondestructive evaluation, computed tomography scanning, was used to quantify the surface morphology as well as capture the as-built geometric dimensions of the cooling schemes. The friction factor and bulk Nusselt number of the coupons were measured using an experimental rig. Pressure loss and heat transfer correlations in the literature were compared with the experimental results from the current coupons and datasets from the literature. Arithmetic mean roughness correlations in the literature struggled to predict the cooling performance of AM channels since the bulk roughness statistic did not capture the overall form of the surface morphology. A combination of root mean square roughness and skewness of the roughness was able to best predict pressure loss and heat transfer for the present samples and those in the literature while being independent of build location, build direction, material, machine, and laser parameters. The maximum absolute error was 25% and the average absolute error was 12% for the friction factor correlation. The maximum absolute error was 39% and the average absolute error was 8% for the Nusselt Number correlation.

Accurate prediction of pressure losses using machine learning for the pipeline transportation of emulsions

One of the significant challenges to designing an emulsion transportation system is predicting frictional pressure losses with confidence. The state-of-the-art method for enhancing reliability in prediction is to employ artificial intelligence (AI) based on various machine learning (ML) tools. Six traditional and tree-based ML algorithms were analyzed for the prediction in the current study. A rigorous feature importance study using RFECV method and relevant statistical analysis was conducted to identify the parameters that significantly contributed to the prediction. Among 16 input variables, the fluid velocity, mass flow rate, and pipe diameter were evaluated as the top predictors to estimate the frictional pressure losses. The significance of the contributing parameters was further validated by estimation error trend analyses. A comprehensive assessment of the regression models demonstrated an ensemble of the top three regressors to excel over all other ML and theoretical models. The ensemble regressor showcased exceptional performance, as evidenced by its high R2 value of 99.7 % and an AUC-ROC score of 98 %. These results were statistically significant, as there was a noticeable difference (within a 95 % confidence interval) compared to the estimations of the three base models. In terms of estimation error, the ensemble model outperformed the top base regressor by demonstrating improvements of 6.6 %, 11.1 %, and 12.75 % for the RMSE, MAE, and CV_MSE evaluation metrics, respectively. The precise and robust estimations achieved by the best regression model in this study further highlight the effectiveness of AI in the field of pipeline engineering.

Pressure-based analysis of rheological equilibrium distances of pumped self-consolidating concrete (SCC)

The influence of pumping on the rheological properties of self-consolidating concrete (SCC) is widely recognized, but there is still limited understanding of its behavior within the pipeline. In this study, we propose a novel approach using equilibrium distances to investigate the evolution of rheological properties along the pipeline. Full-scale horizontal pumping circuits spanning 328 m were established to assess the axial development of SCC's rheological properties. Thirteen mixtures, with water-to-cement (w/c) ratios ranging from 0.22 to 0.27, were pumped at discharge rates varying from 5.77 to 12.69 L/s. Our findings show that for pumping setups and material studied, both the w/c ratio of SCC and the discharge rate significantly affected the influence of rheological equilibrium distances on pressure loss gradient changes. In all tested samples, viscosity values required the entire length of the pipeline to reach post-pumping levels, while yield stress values rapidly achieved their fully developed state upon entering the pipeline. Importantly, the predicted pressure loss displayed a strong correlation with experimental measurements, with an accuracy of 89.42% across all tested mixtures. Our predictive model showed an average improvement of 4.6% in accuracy compared to the linear approach, with the most significant enhancement observed in samples with higher w/c ratios. This research sheds new light on the behavior of SCC during pumping and provides valuable insights for optimizing the pumping process.

A method of predicting the two-phase liquid-liquid flow resistance in a horizontal pipe with a layer of metal foam

The study reported here is experimental. Its aim was to determine the method applicable for prediction of pressure losses of an unstable two-phase liquid-liquid system flow through a horizontal pipe with a short section of the pipe containing a metal foam packing. However, the flow disturbance resulting from the presence of foam does not lead to a change in the type of the mixture (as there is no phase inversion) nor a permanent emulsification of the flow system. The calculation procedure developed in the study takes into account both the peculiarities that accompany the flow of a two-phase liquid-liquid system in an empty pipe (i.e. type of continuous phase, phase slip, hold-up), as well as geometric parameters of the foam skeleton (i.e. cell and pore dimensions, surface roughness of fibers). The results of experimental research were applied for the purposes of determining the specific form of the equations, consistent with the mathematical model adopted and described in detail in this paper. They were conducted for two foams: aluminum and nickel, which were characterized by the same degree of pore packing (PPI20). The mean dimensions of the elements forming metal foams skeletons were determined by computed tomography. The horizontal flow tube had a diameter of 10 mm and the foam packing occupied it only over a a section with a certain length. In the liquid-liquid system pumped to the pipe, the hydrophilic phase was tap water, while the hydrophobic phase was typical machine oil. The adopted range of flux changes of both liquids corresponded to the conditions at which unstable two-phase systems of the W/O, O/W and W+O type were formed in the empty pipe. The pressure loss of the flowing substance was measured in the foam layer. The values of constants and exponents of the adopted model equation were determined separately for single-phase flow and two-phase systems of various types. The results of the statistical evaluation of the performance of the developed dependencies justify their application in the design procedures of selected heat or mass transfer devices. The equations are dimensionless, and therefore, under the conditions of validity, they should also be effective for other liquid-liquid systems, other foams and flow in a pipe with a different diameter. The developed method is based on a new approach to the description of the two-phase flow resistance through the porous material filling the pipe. In addition, it concerns the flow of a liquid-liquid system, which still forms the area that has been tackled in few publications.

Quasi-One-Dimensional Loss Model of Volute Using Boundary Layer Approach for Inward Flow Radial Supercritical CO2 Turbines

Abstract Inward flow radial sCO2 turbines operate at considerably higher speeds than conventional gas or steam turbines making only the low specific speed designs practically realizable. Low-specific speed designs suffer from significantly higher viscous losses in the volute due to long and narrow flow passages. The volute loss in low specific speed designs results in an 8% to 12% efficiency drop, which is approximately 50% of the total loss. The paper proposes a quasi-one-dimensional (quasi-1D) model to estimate the total pressure loss in a volute with acceptable accuracy while consuming negligible computational power compared to a three-dimensional computational fluid dynamics simulation. The model converts the three-dimensional flow in a volute into an equivalent quasi-1D flow. Boundary layer-based momentum integral method is used on the quasi-1D flow path to calculate the total pressure loss. A computer program is developed to implement the proposed model. The accuracy of the model is tested with three-dimensional computational fluid dynamics results in the kW to MW power scale for different boundary conditions. The validation exercise is performed for two volute cross sections—circular and trapezoidal, to check the universality of the model. The model predicts the total pressure loss with less than 10% error for all test conditions. In contrast, a fully developed pipe flow model shows a considerably higher error (∼50%) in total pressure loss prediction for identical flow conditions. The model can also incorporate the effect of surface roughness of the volute. In addition, the model accurately calculates losses under off-design operations.

Numerical Simulation of Taylor—Couette—Poiseuille Flow at Re = 10,000

A fully developed turbulent flow in a concentric annulus, Re =10,000, ri/ro=0.5, with an inner rotating cylinder in the velocity range N=Uω/Ub=0÷4, is studied via a large-eddy simulation. Also, for comparison, simulations by steady-state, unstatiounary RANS k-ω SST (URANS), and Elliptic Blending Model (EBM) were made. The main focus of this study is on the effect of high rotation on the mean flow, turbulence statistics, and vortex structure. Distribution of the tangential velocity and the Reynolds stress tensor change their behaviour at N>0.5∼1. With rotation increases, the production of tangential fluctuation becomes dominant over axial ones and the position of turbulent kinetic energy maximum shifts towards the wall into the buffer zone. URANS and EBM approaches show good agreement with LES in mean flow, turbulent statistics, and integral parameters. The difference in pressure loss prediction between LES and URANS does not exceed 20%, but the average difference is about 11%. The EBM approach underestimates pressure losses up to 9% and on average not more than 5%. Vortex structures are described well by URANS.

Comparative study of the accuracy of friction factor correlations developed for flow of inelastic yield power-law fluids in pipes

An extensive review of the friction factor correlations used for pressure loss prediction of yield power-law (YPL) fluid flow in pipes has been conducted, and the results are summarized in this paper.A comparative study was also conducted to determine the predictive performances of various laminar and turbulent friction factor models developed for YPL fluid flow in pipes. Model predictions of frictional pressure losses were validated by comparing them with the experimentally measured pressure drop data obtained from the flow of several YPL fluids in pipes.Investigations were further extended to determine the impact of the variation of YPL fluid rheological characteristics (resulting from using different rheological characterization methods) on the pressure drop predictions.A wide range of generalized Reynolds numbers (i.e., 20 to 9000, as defined by the API-RP:13D) in a pipe flow configuration was considered in the analyses. The yield stress of the test fluids (determined by using the nonlinear curve fitting technique recommended by the API RP:13D) varied from 0.10 to 0.95 Pa.The results indicated that Hanks and Ricks' model predicted the pressure drop of YPL fluid flow in pipes better than any other models, both in laminar and turbulent flow regimes, matching the experimental data within a ±10% error range.Variations of the YPL model parameters (resulting from using different rheological characterization methods) significantly impacted the pressure drop predictions. Using YPL model parameters obtained from the non-iterative dual power law (DPL) approximation method (as recommended by API-RP:13D) and Hanks and Ricks' model yielded the most accurate pressure drop predictions for the pipe flow of YPL fluids.

CFD Simulation of Air-Glass Beads Fluidized Bed Hydrodynamics

The hydrodynamic behaviour of air-glass beads bubbling fluidized bed reactor containing spherical glass beads is numerically studied, using OpenFoam v7 CFD software. Both Gidaspow and Syamlal-O'Brien drag models are used to calculate momentum exchange coefficients. Simulation predictions of pressure loss, bed expansion rate, and air volume fraction parameters were compared and validated using data, existing in the literature obtained experimentally and performed by other numerical softwares. Pressure loss and rate of bed expansion were calculated with relative root mean square error (RMSE) equal to 0.65 and 0.095 respectively; Syamlal-O'Brien model is considered more accurate than Gidaspow model. Hence, numerical model reliability developed on OpenFoam was also proved. The hydrodynamic aspect study of the fluidized bed reactor was then performed, to analyse the impact of inlet air velocity (U) on particles motion. It was revealed that with U increment, air and glass beads axial velocities increase in the reactor centre and decrease in the sidewalls. Thus, a greater particle bed expansion is induced and the solid particles accumulated highly on the reactor sidewalls. In general, with the increase of U, the solid volume fraction decreases from 0.63 to 0.58 observed at 0.065 m/s and 0.51 m/s, respectively.

Experimental study on the effect of liquid properties on fluid behavior and liquid loading in vertical natural gas wells

Liquid loading is one of the major challenges for natural gas wells, as it can decrease and eventually cease the production of hydrocarbons. Characterizing liquid loading in gas wells and quantifying flow dynamics throughout this process is crucial. The literature shows a lack of experiments for oil-air low liquid loading flow, especially in vertical pipes. This demonstrates a lack of experimental data to comprehend the effect of liquid properties on two-phase flow behavior. In order to simulate a vertical natural gas well, oil-air tests were carried out in this work in a vertical pipe with a 0.0508-m ID (Inner-Diameter) under low liquid loading conditions. The aim of this study is to better comprehend the effect of liquid characteristics on flow behavior and the onset of liquid loading.The results of the experiments reveal that changing the liquid phase from water to oil reduces pressure loss, liquid holdup, and the surface gas velocity (vSg) at which liquid loading occurs. Liquid holdup and pressure loss of the water-air and oil-air flow with medium gas rates show notable variances within the churn flow. Additionally, compared to the minimum-pressure drop technique, the positive pressure technique offers considerably more reliable predictions for the start of liquid loading.Two models—the unified Tulsa University Fluid Flow Projects (TUFFP) and OLGA—are used to investigate the flow pattern, liquid holdup, and pressure loss predictions. The liquid film reverse, liquid droplet models, and the inflection point technique were compared to experimental data for similar liquid loading onset models by Alsanea et al. (2022). For the data in this investigation, the OLGA model and Coleman's correlation perform the best at predicting the onset of liquid loading. Given that both the unified model and OLGA use slug flow models, the results show that a separate model must be created for churn flow to accurately estimate the pressure drop and liquid holdup.

Prediction of nonlinear pumping pressure loss of concrete induced by rheological property changes

The pumping pressure loss of fresh concrete has traditionally been modeled as a linear function of the pumping distance. However, previous studies have suggested that this relationship is nonlinear in nature. This research has identified that the nonlinearity is due to changes in the rheological properties of fresh concrete during pumping. In this study, a new prediction equation has been proposed for the loss of pumping pressure for concrete mixtures with w/c ratios between 0.17 and 0.46, and an equivalent horizontal pipe length between 328 and 912 m. The equation provides a linear approximation of the nonlinear relationship of pumping pressure loss. To account for the effect of rheological changes during pumping, an empirical coefficient related to the initial slump flow of the concrete has been incorporated. The new function can improve the prediction accuracy of pressure loss by 25 % and 4.2 % for horizontal and vertical pumping, respectively.

Experimental and numerical research on flow characteristics of inlet particle separator for aero-engine under the influence of water film

An aero-engine must be able to operate in all-weather conditions, which requires the aircraft to be safe throughout the flight even in bad weather. Excessive intake of rainwater can induce stall and surge of compressor and flameout of combustion chamber, which will lead to the loss of power of the engine. In rainy weather, water come into the engine inlet protection device, which directly determines the compressor inlet conditions and will further affect the compressor working condition and the matching features. In this paper, special attention was paid to the experimental characteristics of aero turbo-shaft engine inlet particle separator (IPS) and the numerical study employing ANSYS-CFX under water spraying condition. Based on the phenomenon of water film forming on the wall surface of the IPS and the experimental data under different water spraying conditions, combined with the predictions from CFD study, an empirical model of water film flow on the wall surface has been developed. The results indicate that in the case of high water ingestion, droplets will inevitably form water film on the wall after entering the IPS. Due to the viscous resistance of wall water film and its influence on the airflow boundary layer, the flow state inside the IPS will change. By establishing a wet wall water film model, the flow characteristics near the wall are closer to the experimental state. The total pressure loss prediction error was reduced from 24.8% to 5.2% and 26.4% to 5.7% under the uniform water spraying rate of 2.93% and 4.84%, respectively.

Validation of computational fluid dynamics simulations for determining pressure loss coefficients of ventilation components

Ventilation systems include a variety of components for which necessary pressure loss data is often unavailable. Computational fluid dynamics simulations could substitute for expensive measurements, but validation simulations with suitable data are crucial to assess model uncertainties. Existing CFD validation studies either did not focus specifically on pressure losses, only covered few components, or did not include recent developments in turbulence modelling. In the present work, 33 bends, 4 gates and 2 tees were simulated using a consistent approach. Computational fluid dynamics simulations were validated with published data: rectangular high-edge and wide-edge bends from the experimental dataset of Sprenger, gates and diverging tees from the SMACMA guide. The considered flows cover important basic flow phenomena: deflection, splitting and flow separation. The 39 components were simulated with three turbulence models at 14 Reynolds numbers. The simulations predicted pressure loss coefficients accurately for various components. Cases with strong flow separation regions were most challenging. The model prediction uncertainty was assessed by carrying out simulations with three selected turbulence models. As in the experimental data from Sprenger, the simulations showed a distinct dependence of pressure loss coefficients on the Reynolds number for bends. In contrast, for abrupt deflections and flow separation at sharp edges, the Reynolds number dependency was minor. Technical pressure loss data of ductwork components is needed for the dimensioning, optimisation, and energy assessment of ventilation systems. The present validation study assesses the present state of the art of CFD simulations to determine pressure loss coefficients and the resulting prediction uncertainties.

Mathematical Modeling Study of Pressure Loss in the Flow Channels of Additive Manufacturing Aviation Hydraulic Valves

The application of additive manufacturing in the field of aviation hydraulics greatly improves the design freedom of hydraulic valve internal flow channels. Pressure loss in hydraulic valve internal flow channels is a primary factor that designers need to consider, and the rapid prediction of pressure loss is very helpful for flow channel design. At present, most studies only focus on how much the pressure loss in an additive manufacturing (AM) hydraulic channel is reduced compared with an original hydraulic channel, and a mathematical model of pressure loss in an AM curved channel is still lacking. In this paper, the pressure loss in a curved flow channel was firstly studied, and the main parameters affecting the pressure loss were determined using the dimensionless analysis method. Using computational fluid dynamics simulation, the relationships between the flow channel diameter, the flow channel length, the flow channel curvature radius, the fluid velocity and pressure loss were studied. According to the multiple regression analysis method, the mathematical model of pressure loss in aviation hydraulic channels was developed, and the model was solved based on the orthogonal experimental results. The pressure loss in the flow channel samples fabricated using selective laser melting was tested, and the results showed that the average error between the test results and the mathematical model calculation results was 7.72%. This model can be used to quickly predict the pressure loss in curved flow channels in the aviation hydraulic field.

Numerical modeling of laminar and turbulent annular flows of power-law fluids in partially blocked geometries

The presence of cuttings bed in deviated wellbores has an undesirable effect on wellbore hydraulics by reducing the open flow area. In addition, pipe eccentricity affects the annular frictional pressure gradient under such configurations. The lack of practical correlations to account for the combined effects of cuttings bed and eccentricity on frictional pressure gradient of power-law fluids is the major motivation of this study. Thus, the effect of partially blocked eccentric annuli on frictional pressure gradient of power-law fluids is investigated. A numerical model is first developed to realize the laminar and turbulent annular flow of power-law fluids in eccentric configurations. The numerical solution of the governing equations is pursued using the finite difference method. The results of our numerical model are verified through comparisons with the published results of frictional pressure gradients in the literature. The numerical results indicate that with an increase in cuttings bed height the frictional pressure gradient can increase exponentially. Numerous simulation scenarios are considered for the flow of power-law fluids in partially blocked eccentric annuli. Then, the simulation results are fitted using regression analysis to obtain explicit correlations for the prediction of laminar and turbulent frictional pressure losses. The proposed correlations are essential for an accurate estimation of the annular frictional pressure gradient and equivalent circulating density, which ensures safe and optimized drilling operations.