scholarly journals A Hybrid Computational and Analytical Model of Inline Drip Emitters

2018 ◽  
Author(s):  
Jaya Narain ◽  
Amos G. Winter
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Flow Behavior ◽  
Applied Pressure ◽  
Computational Time ◽  
Matrix Formulation ◽  
Element Analysis ◽  
Line Load ◽  
Variable Resistor ◽  
Constant Flow Rate

This paper details a hybrid computational and analytical model to predict the performance of inline pressure-compensating (PC) drip irrigation emitters. The term inline refers to flow control devices mounted within the irrigation tubing. Pressure-compensating emitters deliver a relatively constant flow rate over a range applied pressure to accurately meter water to crops. Flow rate is controlled within the emitter by directing the water through a tortuous path (which imposes a fixed resistance), and then through a variable resistor composed of a flexible membrane that deflects under changes in pressure, restricting the flow path. An experimentally validated computational fluid dynamics (CFD) model was used to predict flow behavior through tortuous paths, and a pressure resistance parameter was derived to represent the pressure drop with a single variable. The bending and shearing mechanics of the membrane were modeled analytically and refined for accuracy by deriving a correction factor using finite element analysis. A least-squares matrix formulation that calculates the force applied by a line load of any shape, along which there is a prescribed deflection applied on a rectangular membrane, was derived and was found to be accurate to within one percent. The applicability of the assumption of locally fully developed flow through the pressure compensating chamber in a drip emitter was analyzed. The combined hybrid computational-analytical model reduces the computational time of modeling drip emitter performance from days to less than 30 minutes, dramatically lowering the time required to iterate and select optimal designs. The model was validated using three commercially available drip emitters, rated at 1.1, 2, and 3.8 L/hr. For each, the model predicted the flow rate with an error of twenty percent or less, as compared to the emitter performance published by the manufacturer.

scholarly journals A Hybrid Computational and Analytical Model of Inline Drip Emitters

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Jaya Narain ◽  
Amos G. Winter V
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Flow Behavior ◽  
Computational Time ◽  
Matrix Formulation ◽  
Element Analysis ◽  
Constant Flow Rate ◽  
Patch Load ◽  
Pressure Resistance ◽  
Time Required

This paper details a hybrid computational and analytical model to predict the performance of inline pressure compensating drip irrigation emitters. Pressure compensating emitters deliver a constant flow rate over a range of applied pressures to accurately meter water to crops. Flow rate is controlled within the emitter via a fixed resistance tortuous path, and a variable flow resistance composed of a flexible membrane that deflects under changes in pressure, restricting the flow path. A pressure resistance parameter was derived using an experimentally validated computational fluid dynamics (CFD) model to describe the flow behavior in tortuous paths. The bending mechanics of the membrane were modeled analytically and refined by deriving a correction factor using finite element analysis (FEA). A matrix formulation that calculates the force applied by a line or a patch load of any shape on a rectangular membrane, along which there is a prescribed deflection, was derived and was found to be accurate to be 1%. The combined hybrid computational–analytical model reduces the computational time of modeling emitters from hours to less than 30 min, dramatically lowering the time required to iterate and select optimal designs. The model was validated experimentally using three commercially available drip emitters and was accurate to within 12% of the experimental results.

scholarly journals Improving the Hydraulic Effects Resulting from the Use of a Submerged Biofiter to Enhance Water Quality in Polluted Streams

2021 ◽  
Vol 18 (23) ◽  
pp. 12351
Author(s):  
Atef A. El-Saiad ◽  
Hany F. Abd-Elhamid ◽  
Zeinab I. Salama ◽  
Martina Zeleňáková ◽  
Erik Weiss ◽  
...  
Keyword(s):  
Water Quality ◽  
Flow Rate ◽  
Water Depth ◽  
Empirical Equation ◽  
Flow Behavior ◽  
The Self ◽  
Constant Flow ◽  
Purification Process ◽  
Constant Flow Rate ◽  
Case Comparison

Water scarcity is one of the most serious problems facing many countries. In addition, water pollution could lose more water. A submerged biofilter (SB) is used to enhance the self-purification process in polluted streams. However, most previous studies have focused on the efficiency of SB to remove pollutants and there is a lack of studies investigating the hydraulic changes in streams. The current paper aimed to study the hydraulic effects of SB on the flow behavior in streams and how to improve it. An empirical equation for determining the flow rate through SB was developed. Different cases were studied to improve the hydraulic effects resulting from the use of SB. The effect of increasing SB length was tested using different SB lengths. The results showed that increasing the length increased the upstream water depth (h1) and relative heading up (h1/h2). In the second case, comparison between continuous and fragmented SB was tested. The results showed that a fragmented biofilter increased the upstream water depth and the relative heading up. Case three tested the effect of SB height. Different SB heights were tested with a fixed length and constant flow rate. The results revealed that the upstream water depth and relative heading up decreased when the biofilter height decreased. Case four tested the effect of SB with a fixed volume and constant flow rate. In this case, the length and height of SB were changed where the volume was fixed. The results showed that the relative heading up decreased when the SB height decreased and the length increased, which revealed that the SB height can improve the hydraulic impacts. Finally, the use of SB to improve the water quality in polluted streams led to an increase of the relative heading up, which can be reduced by decreasing the height of SB.

Transient Mechanistic Model for Slug Damper/Gas-Liquid Cylindrical Cyclone (GLCC©) Compact Separator System

2009 ◽  
Author(s):  
E. Pereyra ◽  
L. Gomez ◽  
R. Mohan ◽  
O. Shoham ◽  
G. Kouba
Keyword(s):  
Flow Rate ◽  
Dynamic Models ◽  
Transient Flow ◽  
Flow Behavior ◽  
Mechanistic Model ◽  
Fixed Time ◽  
Flow Conditions ◽  
Time Step ◽  
Constant Flow Rate ◽  
Cylindrical Cyclone

A dynamic model and a simulator have been developed for the Gas-Liquid Cylindrical Cyclone/Slug Damper (GLCC©-SD) system, for the prediction of its flow behavior under transient slugging flow conditions. Separate dynamic models and simulators are developed for the GLCC© and the SD units, which are integrated together with a slug generator model/simulator into an overall model/simulator for the GLCC©-SD system. Two numerical schemes are utilized for the developed integrated simulator, namely, fixed time step and variable time step schemes. Simulation examples are presented for the GLCC©, SD and integrated GLCC©-SD system, for the prediction of their performance under transient flow conditions. The GLCC©-SD simulation results demonstrate clearly the advantage of this system in dampening and smoothing the liquid flow rate under slug flow conditions, providing fairly constant flow rate at the GLCC© outlet liquid leg. The developed GLCC©-SD simulator can be extended to other separators, such as the gravity vessel separators and liquid hydrocyclones.

scholarly journals EFFECT OF TUBE PITCH ON HEAR TRANSFER IN SPRINKLED TUBE BUNDLE

2015 ◽  
Vol 55 (5) ◽  
pp. 329 ◽  
Author(s):  
Petr Kracík ◽  
Jiří Pospíšil
Keyword(s):  
Flow Rate ◽  
Tube Bundle ◽  
Thin Liquid Film ◽  
Thermal Conditions ◽  
Tube Length ◽  
Falling Film ◽  
Constant Flow Rate ◽  
Physical Conditions ◽  
The Individual ◽  
Tube Pitch

Water flowing on a sprinkled tube bundle forms three basic modes: the Droplet mode (the liquid drips from one tube to another), the Jet mode (with an increasing flow rate, the droplets merge into a column) and the Membrane (Sheet) mode (with a further increase in the flow rate of the falling film liquid, the columns merge and create sheets between the tubes. With a sufficient flow rate, the sheets merge at this stage, and the tube bundle is completely covered by a thin liquid film). There are several factors influencing both the individual modes and the heat transfer. Beside the above-mentioned falling film liquid flow rate, these are for instance the tube diameters, the tube pitches in the tube bundle, or the physical conditions of the falling film liquid. This paper presents a summary of data measured at atmospheric pressure, with a tube bundle consisting of copper tubes of 12 millimetres in diameter, and with a studied tube length of one meter. The tubes are situated horizontally one above another at a pitch of 15 to 30 mm, and there is a distribution tube placed above them with water flowing through apertures of 1.0mm in diameter at a 9.2mm span. Two thermal conditions have been tested with all pitches: 15 °C to 40 °C and 15 °C to 45 °C. The temperature of the falling film liquid, which was heated during the flow through the exchanger, was 15 °C at the distribution tube input. The temperature of the heating liquid at the exchanger input, which had a constant flow rate of approx. 7.2. litres per minute, was 40 °C, or alternatively 45 °C.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

Evaluation of web reinforcements in prestressed concrete box girders through shear-transverse bending domains

2020 ◽  
pp. 136943322098170
Author(s):  
Michele Fabio Granata ◽  
Antonino Recupero
Keyword(s):  
Analytical Model ◽  
Prestressed Concrete ◽  
3D Analysis ◽  
Box Girders ◽  
Element Analysis ◽  
Cross Sectional ◽  
Interaction Domains ◽  
Global And Local ◽  
Resultant Forces

In concrete box girders, the amount and distribution of reinforcements in the webs have to be estimated considering the local effects due to eccentric external loads and cross-sectional distortion and not only the global effect due to the resultant forces of a longitudinal analysis: shear, torsion and bending. This work presents an analytical model that allows designers to take into account the interaction of all these effects, global and local, for the determination of the reinforcements. The model is based on the theory of stress fields and it has been compared to a 3D finite element analysis, in order to validate the interaction domains. The results show how the proposed analytical model allows an easy and reliable reinforcement evaluation, in agreement with a more refined 3D analysis but with a reduced computational burden.

scholarly journals Pressure Equilibrium Time of a Cyclic-Olefin Copolymer

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2309
Author(s):  
Benedikt Roth ◽  
Dietmar Drummer
Keyword(s):  
Dynamic Compression ◽  
Flow Behavior ◽  
Superposition Principle ◽  
Applied Pressure ◽  
Thermal Shrinkage ◽  
Compression Rate ◽  
Rate Dependency ◽  
Equilibrium Time ◽  
Simulation Techniques ◽  
Pressure Equilibrium

Integrative simulation techniques for predicting component properties, based on the conditions during processing, are becoming increasingly important. The calculation of orientations in injection molding, which, in addition to mechanical and optical properties, also affect the thermal shrinkage behavior, are modeled on the basis of measurements that cannot take into account the pressure driven flow processes, which cause the orientations during the holding pressure phase. Previous investigations with a high-pressure capillary rheometer (HPC) and closed counter pressure chamber (CPC) showed the significant effect of a dynamically applied pressure on the flow behavior, depending on the temperature and the underlying compression rate. At a constant compression rate, an effective pressure difference between the measuring chamber and the CPC was observed, which resulted in a stop of flow through the capillary referred to as dynamic compression induced solidification. In order to extend the material understanding to the moment after dynamic solidification, an equilibrium time, which is needed until the pressure signals equalize, was evaluated and investigated in terms of a pressure, temperature and a possible compression rate dependency in this study. The findings show an exponential increase of the determined equilibrium time as a function of the holding pressure level and a decrease of the equilibrium time with increasing temperature. In case of supercritical compression in the area of a dynamic solidification, a compression rate dependency of the determined equilibrium times is also found. The measurement results show a temperature-invariant behavior, which allows the derivation of a master curve, according to the superposition principle, to calculate the pressure equilibrium time as a function of the holding pressure and the temperature.

scholarly journals Image-based semi-multiscale finite element analysis using elastic subdomain homogenization

Meccanica ◽  
2021 ◽  
Author(s):  
J. Jansson ◽  
K. Salomonsson ◽  
J. Olofsson
Keyword(s):  
Finite Element ◽  
Analytical Method ◽  
Effective Properties ◽  
Reference Model ◽  
Computational Time ◽  
Component Level ◽  
Element Analysis ◽  
Model Fidelity ◽  
Multiscale Finite Element ◽  
Anisotropic Elastic

AbstractIn this paper we present a semi-multiscale methodology, where a micrograph is split into multiple independent numerical model subdomains. The purpose of this approach is to enable a controlled reduction in model fidelity at the microscale, while providing more detailed material data for component level- or more advanced finite element models. The effective anisotropic elastic properties of each subdomain are computed using periodic boundary conditions, and are subsequently mapped back to a reduced mesh of the original micrograph. Alternatively, effective isotropic properties are generated using a semi-analytical method, based on averaged Hashin–Shtrikman bounds with fractions determined via pixel summation. The chosen discretization strategy (pixelwise or partially smoothed) is shown to introduce an uncertainty in effective properties lower than 2% for the edge-case of a finite plate containing a circular hole. The methodology is applied to a aluminium alloy micrograph. It is shown that the number of elements in the aluminium model can be reduced by $$99.89\%$$ 99.89 % while not deviating from the reference model effective material properties by more than $$0.65\%$$ 0.65 % , while also retaining some of the characteristics of the stress-field. The computational time of the semi-analytical method is shown to be several orders of magnitude lower than the numerical one.

scholarly journals Quantitative Monitoring of Dynamic Blood Flows Using Coflowing Laminar Streams in a Sensorless Approach

2021 ◽  
Vol 11 (16) ◽  
pp. 7260
Author(s):  
Yang Jun Kang
Keyword(s):  
Blood Flow ◽  
Flow Rate ◽  
Blood Viscosity ◽  
Measurement Errors ◽  
Present Method ◽  
Test Fluid ◽  
Constant Flow Rate ◽  
Rbc Aggregation ◽  
Sinusoidal Flow ◽  
Analytical Expressions

Determination of blood viscosity requires consistent measurement of blood flow rates, which leads to measurement errors and presents several issues when there are continuous changes in hematocrit changes. Instead of blood viscosity, a coflowing channel as a pressure sensor is adopted to quantify the dynamic flow of blood. Information on blood (i.e., hematocrit, flow rate, and viscosity) is not provided in advance. Using a discrete circuit model for the coflowing streams, the analytical expressions for four properties (i.e., pressure, shear stress, and two types of work) are then derived to quantify the flow of the test fluid. The analytical expressions are validated through numerical simulations. To demonstrate the method, the four properties are obtained using the present method by varying the flow patterns (i.e., constant flow rate or sinusoidal flow rate) as well as test fluids (i.e., glycerin solutions and blood). Thereafter, the present method is applied to quantify the dynamic flows of RBC aggregation-enhanced blood with a peristaltic pump, where any information regarding the blood is not specific. The experimental results indicate that the present method can quantify dynamic blood flow consistently, where hematocrit changes continuously over time.

scholarly journals Practical Prediction of the Boil-Off Rate of Independent-Type Storage Tanks

2021 ◽  
Vol 9 (1) ◽  
pp. 36
Author(s):  
Dong-Ha Lee ◽  
Seung-Joo Cha ◽  
Jeong-Dae Kim ◽  
Jeong-Hyeon Kim ◽  
Seul-Kee Kim ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Environmentally Friendly ◽  
Fuel Tank ◽  
Computational Time ◽  
Insulation Material ◽  
Element Analysis ◽  
Vertical Temperature Profile ◽  
Space Efficiency ◽  
Key Aspects

Because environmentally-friendly fuels such as natural gas and hydrogen are primarily stored in the form of cryogenic liquids to enable efficient transportation, the demand for cryogenic fuel (LNG, LH) ships has been increasing as the primary carriers of environmentally-friendly fuels. In such ships, insulation systems must be used to prevent heat inflow to the tank to suppress the generation of boil-off gas (BOG). The presence of BOG can lead to an increased internal pressure, and thus, its control and prediction are key aspects in the design of fuel tanks. In this regard, although the thermal analysis of the phase change through a finite element analysis requires less computational time than that implemented through computational fluid dynamics, the former is relatively more error-prone. Therefore, in this study, a cryogenic fuel tank to be incorporated in ships was established, and the boil-off rate (BOR), measured considering liquid nitrogen, was compared with that obtained using the finite element method. Insulation material with a cubic structure was applied to the cylindrical tank to increase the insulation performance and space efficiency. To predict the BOR through finite element analysis, the effective thermal conductivity was calculated through an empirical correlation and applied to the designed fuel tank. The calculation was predicted to within 1% of the minimum error, and the internal fluid behavior was evaluated by analyzing the vertical temperature profile according to the filling ratio.

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