Fluid Mechanics Laboratory Research Articles

Experimental apparatus to test air trap valves

It is known that the presence of trapped air within water distribution pipes can lead to irregular operation or even damage to the distribution systems and their components. The presence of trapped air may occur while the pipes are being filled with water, or while the pumping systems are in operation. The formation of large air pockets can produce the water hammer phenomenon, the instability and the loss of pressure in the water distribution networks. As a result, it can overload the pumps, increase the consumption of electricity, and damage the pumping system. In order to avoid its formation, all of the trapped air should be removed through "air trap valves". In Brazil, manufacturers frequently have unreliable sizing charts, which cause malfunctioning of the "air trap valves". The result of these malfunctions causes accidents of substantial damage. The construction of a test facility will provide a foundation of technical information that will be used to help make decisions when designing a system of pipelines where "air trap valves" are used. To achieve this, all of the valve characteristics (geometric, mechanic, hydraulic and dynamic) should be determined. This paper aims to describe and analyze the experimental apparatus and test procedure to be used to test "air trap valves". The experimental apparatus and test facility will be located at the University of Campinas, Brazil at the College of Civil Engineering, Architecture, and Urbanism in the Hydraulics and Fluid Mechanics laboratory. The experimental apparatus will be comprised of various components (pumps, steel pipes, butterfly valves to control the discharge, flow meter and reservoirs) and instrumentation (pressure transducers, anemometer and proximity sensor). It should be emphasized that all theoretical and experimental procedures should be defined while taking into consideration flow parameters and fluid properties that influence the tests.

Flow-induced vibration of two circular cylinders in tandem arrangement. Part 2: Suppression of vibrations

This paper presents an experimental investigation on suppression of cross-flow vibrations of two circular cylinders in tandem arrangement, conducted at the fluid mechanics laboratory of Kitami Institute of Technology, Japan. To suppress the vibrations of the cylinders, tripping wires were deployed, attached symmetrically about the leading stagnation lines of the cylinders. Five spacing ratios were examined, i.e., L/ D=0.1, 0.3, 0.8, 2.0 and 3.2 ( L is the gap spacing between the two cylinders; D is the diameter of cylinder), which are representative for five Regimes I (0.1≤ L/ D<0.2), II (0.2≤ L/ D<0.6), III (0.6≤ L/ D<2), IV (2≤ L/ D<2.7) and V ( L/ D≥2.7), respectively, as classified in Part 1 [Kim et al., 2009. Flow-induced vibrations of two circular cylinders in tandem arrangement (part 1: characteristics of vibration). Journal of Wind Engineering and Industrial Aerodynamics, submitted together for publication]. Tripping wire position θ measured from the leading stagnation lines of the cylinders was changed from 20° to 60° to determine the optimum range of θ for suppressing structural vibrations. The shear layers separated from the two cylinders were investigated based on flow visualization. The main findings are: (i) the flow-induced vibration on the two cylinders depends strongly on θ, (ii) at θ=20–30° the vibrations on both cylinders are almost completely suppressed for all regimes except V, and (iii) for θ≥40° the vibration amplitudes of both cylinders are considerably larger than those of the plain cylinders, particularly at θ=40°, where the vibration of the upstream cylinder becomes divergent.

Free vibration of two identical circular cylinders in staggered arrangement

An investigation on flow-induced response characteristics of two identical circular cylinders in staggered arrangement is conducted in the fluid mechanics laboratory of Kitami Institute of Technology, Japan. Each cylinder was two-dimensional, spring mounted, and allowed to vibrate independently in the cross-flow direction. Measurements were conducted at stagger angle α = 5°, 10°, 15°, 25°, 45° and 60°, L/D ranging from 0.1 to 3.2, with ΔL/D = 0.1, where L is the gap width between the cylinders, and D is the diameter of a cylinder. At each position (α, L/D) of the cylinders, dependence of vibration-amplitude-to-diameter ratio a/D on reduced velocity Ur (= U∞/(fnD)) is examined, where U∞ is the free-stream velocity and fn is the natural frequency of the cylinder. There are seven cylinder-response patterns, depending on whether vortex-excited and/or galloping vibrations of the cylinders are generated, in the range α = 5°–60°, L/D = 0.1–3.2 and Ur = 1.5–26. Pattern I corresponds to no generation of vortex-excited or galloping vibration of either cylinder. In Pattern II the upstream cylinder does not experience vortex-excited or galloping vibration, but the downstream one experiences a galloping vibration. Pattern III involves both vortex-excited and galloping vibrations of the downstream cylinder and only galloping vibration of the upstream cylinder. Pattern IV is associated with generation of vortex-excited vibration of both cylinders at the same Ur range. Pattern V refers to the case where the downstream cylinder experiences vortex-excited vibration, but the upstream cylinder does not. Pattern VI is characterized by vortex-excited vibration of the downstream cylinder in two regimes of Ur, whereas that of the upstream cylinder occurs in one regime only. In Pattern VII the upstream and downstream cylinders experience vortex-excited vibration at two different Ur regimes, respectively. The L/D regime of the vibration patterns generated at each α is identified.

Effect of Side Wind on a Simplified Car Model: Experimental and Numerical Analysis

A prior analysis of the effect of steady cross wind on full size cars or models must be conducted when dealing with transient cross wind gust effects on automobiles. The experimental and numerical tests presented in this paper are performed on the Willy square-back test model. This model is realistic compared with a van-type vehicle; its plane underbody surface is parallel to the ground, and separations are limited to the base for moderated yaw angles. Experiments were carried out in the semi-open test section at the Conservatoire National des Arts et Métiers, and computations were performed at the Ecole Centrale de Nantes (ECN). The ISIS-CFD flow solver, developed by the CFD Department of the Fluid Mechanics Laboratory of ECN, used the incompressible unsteady Reynolds-averaged Navier–Stokes equations. In this paper, the results of experiments obtained at a Reynolds number of 0.9×106 are compared with numerical data at the same Reynolds number for steady flows. In both the experiments and numerical results, the yaw angle varies from 0 deg to 30 deg. The comparison between experimental and numerical results obtained for aerodynamic forces, wall pressures, and total pressure maps shows that the unsteady ISIS-CFD solver correctly reflects the physics of steady three-dimensional separated flows around bluff bodies. This encouraging result allows us to move to a second step dealing with the analysis of unsteady separated flows around the Willy model.

Experimental Apparatus for Measurements of Two-Phase Slug Flow Pressure Drop in a T-Junction

An experimental test loop system was designed, developed, and constructed to study the two-phase flow field in the undergraduate fluid mechanics laboratory. The purpose of this experimental apparatus is to measure the pressure drop of a two-phase mixture in a tee-junction. This paper describes a fluid mechanics experiment designed for undergraduate students to examine the pressure differences through a T-junction of an air–water mixture in slug two-phase flow regime with equal-sided diameters. This can be carried out at different inlet qualities and extraction rates. Sample results are presented.

Effets d'échelle pour des écoulements turbulents autour de dragues

ABSTRACT The study describes a synthesis of a numerical and experimental work performed during the European research project EFFORT (European Full-scale FlOw Research and Technology) aiming at studying scale effects for hulls of high geometrical complexity by numerical and experimental means. During this project, the CFD group of Fluid Mechanics Laboratory (UMR6598) has performed a complete study of scale and appendage effects on an hopperdredger “Uilenspiegel”. These computations are discussed and compared with available local wake measurements obtained within EFFORT.

Experimental and numerical investigations of the flow around an oar blade

This article aims at verifying the capabilities of a Reynolds-Averaged Navier-Stokes Equations (RANSE) solver (ISIS-CFD, developed at the Fluid Mechanics Laboratory of Ecole Centrale de Nantes [LMF]) to accurately compute the flow around an oar blade and to deduce the forces on it and other quantities such as efficiency. This solver is structurally capable of computing the flow around any blade shape for any movement in six degrees of freedom, both when the blade pierces the free surface of the water and when it does not. To attempt a first validation, a computation was performed for a simplified case chosen among those for which experimental results are available at LMF. If results prove satisfactory for a simplified blade shape and for a movement that respects the main characteristics of blade kinematics, then the solver could be used for real oars and more realistic kinematics. First, the experimental setup is considered, and the objectives, methodologies, and procedures are elucidated. The choice of the test case for numerical validation is explained, i.e., a plane rectangular blade with a constant immersion and a specified movement deduced from analogy with tests on propellers. Next, the numerical framework is presented and the Navier-Stokes solver and methods for handling multifluid flows and moving bodies are described. Lastly, numerical results are compared with experimental data, highlighting an encouraging agreement and proving the relevance and the complementarity of both approaches.

Does the lack of hands-on experience in a remotely delivered laboratory course affect student learning?

Educators question whether performing a laboratory experiment as an observer (non-hands-on), such as conducted in a distance education context, can be as effective a learning tool as personally performing the experiment in a laboratory environment. The present paper investigates this issue by comparing the performance of distance education students with their on-campus counterparts in a junior-level fluid mechanics laboratory course over a three semester period. Using digital recording methods, the on-campus versions of the laboratory experiments were formatted to accommodate distance-education students who did not have access to campus facilities. This paper compares the assessment of student performance in demonstrating both learning of technical concepts and the ability to describe these in an effective written laboratory report.

Wind energy resource assessment in Madrid region

The “Comunidad Autónoma de Madrid” (Autonomous Community of Madrid, in the following Madrid Region), is a region located at the geographical centre of the Iberian Peninsula. Its area is 8.028 km 2, and its population about five million people. The Department of Economy and Technological Innovation of the Madrid Region, together with some organizations dealing on energy saving and other research institutions have elaborated an Energy Plan for the 2004–12 period. As a part of this work, the Fluid Mechanics Laboratory of the Superior Technical School of Industrial Engineers of the Polytechnic University of Madrid has carried out the assessment of the wind energy resources [Crespo A, Migoya E, Gómez Elvira R. La energía eólica en Madrid. Potencialidad y prospectiva. Plan energético de la Comunidad de Madrid, 2004–2012. Madrid: Comunidad Autónoma de Madrid; 2004]; using for this task the WAsP program (Wind Atlas Analysis and Application Program), and the own codes, UPMORO (code to study orography effects) and UPMPARK (code to study wake effects in wind parks). Different kinds of data have been collected about climate, topography, roughness of the land, environmentally protected areas, town and village distribution, population density, main facilities and electric power supply. The Spanish National Meteorological Institute has nine wind measurement stations in the region, but only four of them have good and reliable temporary wind data, with time measurement periods that are long enough to provide representative correlations among stations. The Observed Wind Climates of the valid meteorological stations have been made. The Wind Atlas and the resource grid have been calculated, especially in the high wind resource areas, selecting appropriate measurements stations and using criteria based on proximity, similarity and ruggedness index. Some areas cannot be used as a wind energy resource mainly because they have environmental regulation or, in some cases, are very close to densely populated towns. In the finally selected areas, it is assumed that there are hypothetical wind farms, consisting of 2 MW turbines in appropriate configurations, in which the turbines are about 11 diameters apart. Its energy production will give an estimation of the wind energy potential of the Madrid Region.

Experimental study of hot air dehydration of Sultana grapes

A laboratory drying unit was designed and constructed at Fluid Mechanics Laboratory, University of Patras, Greece, in order to evaluate the essential drying characteristics of various fruits and vegetables. The paper presents results of experiments done in the case of hot air drying of Sultana grapes. Time evolution of measured parameters is cross analyzed and presented in diagrams. Moisture content, drying rates and relative moisture content are calculated and also presented in diagrams. Thin-layer model and Page’s equation were used for modelling the drying of Sultana grapes up to the water moisture content usually required to attain the shelf stability. The drying constants, effective diffusivity of the bed and product constant were evaluated upon the analytical solution of the thin-layer and Page’s equations. The resulted curves were plotted in diagrams and graphically compared with experimental data. A good agreement was found between measurements and Page’s equation prediction. Another aim of this research was to validate the in-house DrySAC numerical code, developed for effective design and control of industrial drying units. A very good agreement between predictions and measurements was found.

Online heat transfer and fluid mechanics laboratory

This paper presents, how multimedia technology can be implemented over the web to enhance the learning experience of students at the University of Oklahoma in a heat transfer and fluid mechanics laboratory. This course module not only introduces fundamental theories about measurement, but also details the experimental setup and procedure for each laboratory assignment. In addition, it has a unique component called “virtual laboratory” in which students can learn the operation of advanced and sophisticated instruments that are not normally available in an undergraduate teaching laboratory. The implementation of “virtual laboratory” can better utilize the resources available while providing an excellent opportunity of learning for students. © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 1–9, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20025

Fluid Mechanics and the Undergraduate Civil Engineer

Mechanics of fluids is one of the fundamental and perhaps one of the more demanding courses for the undergraduate civil engineer. The objectives of this Forum are to foster improvement of the undergraduate level instruction in fluid mechanics and to anchor one of the essential and traditional roles of a teacher therein. With these two objectives in mind, this Forum’s first aspect relates to an imbalance between the use of a library and a fluid mechanics laboratory, and the second aspect relates to the use of peripheral material such as anecdotes, and analogies, and biological and sports links in a classroom. This Forum is based on the author’s teaching experience at the University of the West Indies (UWI) in Trinidad, amidst the educational and geographic background of the Commonwealth Caribbean.

Inside “the system”: engineers, scientists, and the boundaries of social protest in the long 1960s

By the end of the 1960s, many engineers and scientists in the US questioned the social and political dimensions of science and technology. This introspection came as critics assailed science and technology as elements of the militaristic, alienating structure of modern society. Engineers and scientists repudiated, appropriated, or sometimes even acted in concert with these critics. Also relevant, however, in engineers' and scientists' evaluations of their role in society were the emergence of “engineering science,” pre‐existing political ideologies, and simply making a living in a volatile economy. This paper presents dissention from three vantages within the technical community: design engineer Steve Slaby at Princeton University, the Fluid Mechanics Laboratory at the Massachusetts Institute of Technology, and the activist organization Science for the People, located in chapters across the country. These cases differ in the actors' level of political consciousness, their involvement in military research, and the tactics they employed. All, however, suggest cause for reassessment both of the borders between “critics” and “scientists” and of the culture of “total control” ascribed to the era.

An Innovation-Based Fluid Mechanics Design and Fabrication Laboratory

As part of a four-week fluid mechanics laboratory, Mechanical Engineering students were challenged to design and manufacture the least restrictive flow nozzle for a standard test condition within several design constraints. The Nozzle Design Challenge (NDC) combined analysis, design, manufacturing, and experimentation. The positive student responses to the NDC were overwhelming. Formal evaluation of the NDC included the measured nozzle flow rates and the amount of time spent in the laboratory. The highest flow rate nozzle allowed substantially more flow than the nozzle with a 1-inch diameter hole used for demonstration. Every group spent more time in the laboratory than was scheduled, which may indicate high levels of motivation for the project. The examination scores covering the principles learned in this laboratory were compared to the previous semester's students who did not perform the innovation-based design and fabrication project. After blocking out the effects of GPA, the results indicate that the students who undertook the design experience performed significantly better on the examination.

Artefact Study in the Fluids Laboratory

The examination of a washing machine fill valve and subsequent testing and analysis are undertaken as a first fluid mechanics laboratory task. A primary intention in doing this is to put into perspective the role of a fluids engineer at a time in the students career when very little fluid mechanics technology is understood and when analytical lecture content is generally held to occupy too large a proportion of a student's attention in this area.

Validation of a k- ε model based on `experimental results in a thermally stable stratified turbulent boundary layer

A 2D ( k- ε) turbulence model was developed for use with dilatable flows at high Reynolds numbers. A new approach relative to the modelling of the density-velocity correlation term is proposed, and a relation concerning the Prandtl turbulent number was used taking into account both the wall and gravity effects. This model was validated by experimental results obtained at the E.C.L. Fluid Mechanics and Acoustics laboratory on a stable thermally stratified turbulent boundary layer developing at a quickly cooled smooth boundary surface.

Basic Elements in a Fluid Mechanics Laboratory Experience: An Engineering Science Approach

Experiments for a first fluid mechanics course are described. The basic concepts of pressure and velocity as the primitive variables, the control volume equations and the field equations with Reynolds number dependent properties are reinforced in these experiments. The use of such experiments, as the experimental background for future lecture instruction, is emphasized.

Hemodynamics and the Arterial Wall: An Introduction

Research Papers Hemodynamics and the Arterial Wall: An Introduction R. M. Nerem R. M. Nerem Physiological Fluid Mechanics Laboratory, Department of Mechanical Engineering, University of Houston, Houston, Tex. 77004 Search for other works by this author on: This Site PubMed Google Scholar Author and Article Information R. M. Nerem Physiological Fluid Mechanics Laboratory, Department of Mechanical Engineering, University of Houston, Houston, Tex. 77004 J Biomech Eng. Aug 1981, 103(3): 171 (1 pages) https://doi.org/10.1115/1.3138274 Published Online: August 1, 1981 Article history Online: June 15, 2009

Interference effects for groups of stacks

Since code information concerning the static wind loads and wind-induced vibrations of groups of stacks is scarce, a basic study in this field of building aerodynamics is currently in progress in the Fluid Mechanics Laboratory of the Fachhochschule Aachen. For some standard configurations the static wind load in high Reynolds number flow simulated by roughening the model surfaces has been obtained. The experiments for measuring the wind-induced vibrations were conducted in subcritical Reynolds number flows. The influence of platforms on the vibrations of in-line stacks has been investigated.

A user oriented mini-computer system for a fluid mechanics laboratory

This paper describes a user oriented mini-computer system, both software and hardware, that can be used for fluid mechanic experimentation. The problems involved in constructing such a system are discussed and the philosophy behind the user oriented software system is presented. As an example, the implementation of this system for a laser anemometry experiment is presented.