Non-dimensional Method Research Articles

Numerical Analysis of Lab Ventilation on Double Gaseous Polluted Sources

This article uses CFD to study the efficiency of ventilation and pollution discharge of double polluted sources in the lab, and investigate the effect of air exhaust outlet location and air supply velocity on the performance of side ventilation. Using non-dimensional analysis method to analyze change of temperature,velocity with room height, the change of temperature efficiency and pollutants emission efficiency with the air supply velocity. The results show that the efficiencies of temperature and pollutants emission are the highest when h/H=0.175 and v=0.4m/s.

Investigation into the Response of Fully Clamped Circular Steel, Copper, and Aluminum Plates Subjected to Shock Loading

The plastic responses of clamped mild steel, copper, and aluminum circular plates subjected to blast loads are investigated. In this way, extensive experimental results concerning the variations of central deflection and natural strain distributions are presented. The effects of plate thickness, stand-off distance, and material properties on the mid-point deflection, on the deformation profile and on the natural strain distributions are considered. Moreover, the influence of impulse on the mid-point deflection and strain distribution are demonstrated. The applied impulse imparted to the plate was obtained from the recorded motion of the ballistic pendulum. Using the obtained experimental input-output data, closed form mathematical models based on nondimensional analysis and Singular Value Decomposition method have been found. The comparisons of the closed form mathematical models of this work with those in literature illustrate the robustness and the efficacy of this approach.

Variáveis espaço-temporais do andar em velocidade lenta, livre e rápida em crianças de 3 a 8 anos

This study aimed to describe and to verify differences in space-temporal variables during walking at three different speeds (slow, free and fast) among three age groups of children. Thirty-three healthy children were distributed into the following groups: 3-4, 5-6 and 7-8 years. Space-temporal data were normalized by Hof’s (1996) non-dimensional method. There was no difference between age groups at slow, fast or normal walking when considered normalized speed. There were differences between groups of 3-4 and 7-8 years of age at free walking for cadence. No significant differences were found between all age groups for slow, free and fast speed when considered absolute step length. It allows us to say that children from this age prefer to change cadence in order to increase speed. As for temporal parameters the same strategy was identified to increase speed for all age groups: higher single stance and balance time and lower double stance.

Variáveis espaço-temporais do andar em velocidade lenta, livre e rápida em crianças de 3 a 8 anos - doi: 10.4025/reveducfis.v21i4.8309

This study aimed to describe and to verify differences in space-temporal variables during walking at three different speeds (slow, free and fast) among three age groups of children. Thirty-three healthy children were distributed into the following groups: 3-4, 5-6 and 7-8 years. Space-temporal data were normalized by Hof’s (1996) non-dimensional method. There was no difference between age groups at slow, fast or normal walking when considered normalized speed. There were differences between groups of 3-4 and 7-8 years of age at free walking for cadence. No significant differences were found between all age groups for slow, free and fast speed when considered absolute step length. It allows us to say that children from this age prefer to change cadence in order to increase speed. As for temporal parameters the same strategy was identified to increase speed for all age groups: higher single stance and balance time and lower double stance.

Free Vibration Analysis of Arbitrarily Shaped Plates With Smoothly Varying Free Edges Using NDIF Method

The so-called non-dimensional influence function method that was developed by the authors is extended to free vibration analysis of arbitrarily shaped plates with the free boundary condition. A method proposed in this paper can be applied to plates with only smoothly varying boundary shapes. In the proposed method, a local polar coordinate system has been employed at each boundary node to effectively consider the free boundary condition, which is much more complex than the simply supported or clamped boundary condition. The local coordinates system devised allowed us to successfully deal with the radius of curvature involved in the free boundary condition, and, as a result, the accuracy of the proposed method has been reinforced. Finally, verification examples showed that the natural frequency and mode shapes obtained by the proposed method agree excellently with those given by other analytical or numerical methods.

Nondimensional star identification for uncalibrated star cameras

Star identification is the most critical and important process for attitude estimation, given data from any star sensor. The main purpose of the Star Identification (Star-ID) process is to identify the observed/measured stars with the corresponding cataloged stars. The precision of the observed star directions highly depend on the calibrated accuracy of the star camera parameters, mainly the focal length f, and the optical axis offsets (x0, y0). When these parameters are not accurate or when the camera is not well calibrated, the proposed Nondimensional Star-ID method becomes very suitable, because it does not require accurate knowledge of these parameters. The Nondimensional Star-ID method represents a unique tool to identify the stars of uncalibrated or inaccurate parameters cameras. The basic idea derives the identification process from the observed focal plane angles which are, to first order, independent from both the focal length and the optical axis offsets. The adoption of the k-vector range search technique, makes this method very fast. Moreover, it is easy to implement, accurate, and the probability of failing Star-ID is less than 0.1% for typical star tracker design parameters.

Windmilling characteristics of centrifugal-flow turbojets

A new nondimensional method for predicting the windmilling performance of centrifugal flow turbojet engines in flight has been developed. The method incorporates loss correlations to estimate the performance of major engine components. Given basic engine geometry, flight Mach number, and ambient conditions, this method predicts transient and steady-state windmilling performance. Thus, this method can be used during the preliminary design stage when detailed hardware geometry and component performance data are not yet available. A nondimensional time parameter is newly defined, and using this parameter, the transient performance of different types of turbojets (e.g. centrifugal vs. axial) is compared. In addition, the predictions’ sensitivity to loss correlations, slip factors, and inlet ambient temperatures are analyzed.

ディーゼル噴霧特性に関する実験的研究 噴霧到達距離の無次元表示

An experimental work has been carried out to explain the Diesel spray behavior. The measurement is per-formed for the spray tip penetration and the spray angle with three different injection pressures and ambient gas density. The change of ambient gas density has been done with pressured N2 gas and a high density SF6 gas. The density of SF6 gas is about 5.3 times N2 gas at room conditions. The obtained results for spray tip penetration are simplified with non-dimensional form. The form is based on Break-up length and time. As a result, the non-dimensional data with N2 gas fit to a curve that is unaffected with different injection pressure and ambient gas density. Moreovere, the measurement result (penetration and angle) with SF6 gas has been shown same result with N2 gas. Therefore, the potential of the non-dimensional expression method for the spray tip penetration is confirmed.

Nondimensional methods for natural ventilation design

The paper deals with the use of nondimensional graphs for designing the envelopes of naturally ventilated buildings. It is argued that such graphs offer several benefits over conventional procedures i.e. generality, ease and speed of use, wide application and accuracy. The graphs can be generated from theoretical models or from experimental data obtained from a direct measurement of ventilation rates in a wind tunnel model. Examples of graphs are given which cover conventional design conditions and, perhaps more importantly, off-design conditions. The off-design conditions include effects which would normally require a great deal of effort to calculate for a particular building e.g. the effects of adventitious leakage and wind turbulence. With the graphs described a designer can obtain a quick indication of whether such effects are important.

Characteristic features of electron-ion collisions in strong electric fields

The classical motion of an electron in the Coulomb field of an ion and in a uniform external electric field is analyzed. A nondimensionalization method that makes it possible to study electron motion in arbitrarily strong electric fields is proposed. The possible electron trajectories in the plane of motion in a static field are classified. It is noted that, from a practical standpoint, the most interesting trajectories are snakelike trajectories, which are absent in the problem with a weak external field. An adiabatic approximation for transverse electron motions in quasistatic (strong) fields is constructed. A one-dimensional equation of motion is derived that accounts for transverse electron oscillations and the increase in the effective electron mass as an electron approaches an ion. An analytic model is used to calculate the spectra of bremsstrahlung generated by individual electrons. The calculated results are shown to agree well with the results of direct numerical integration of the basic equations. It is predicted that, at frequencies higher than the frequency of the incident light, pronounced peaks can appear in the spectrum of the transverse dipole moment of an electron; as a result, an electron is expected to effectively emit radiation at these frequencies in the direction of the external field.

Nondimensional simulation of influence of toughness of interface on tensile stress–strain behavior of unidirectional microcomposite

Abstract For description of the stress–strain curve, variation of Young's modulus with increasing applied strain and fracture morphology of composite, a nondimensional shear lag method combined with a Monte Carlo simulation procedure was proposed, in which the statistics of the occurrence of damages such as breakage of components (fiber and matrix) and debonding of interface, mechanical interactions among the damaged and undamaged portions and variation of the geometry of location of the damages with increasing applied strain, are incorporated. The proposed method was applied to microcomposite with different interfacial toughness, and variations of the order and location of occurrence of damages, stress–strain curve and fracture morphology with varying interfacial toughness were shown.

Approximate Solution of Interactions among Spatially Distributed Broken Fiber, Matrix and Interface in the Progress of Interfacial Debonding in Multifilamentary Unidirectional Composites.

In order to describe the relationship of mesoscopic phenomena of interfacial debonding and breakage of fiber and matrix to the macroscopic stress-strain curve of unidirectional composites, an approximate nondimensional solution method was presented using a two-dimensional model. By applying this method to several examples in which the species and locations of broken components were varied, the following features were revealed: (a) fiber-breakage-induced debonding occurs at a lower strain than the matrix-breakage-induced one; (b) the overall debonding is hastened due to mechanical intractions under the existence of many broken fibers and matrices; (c) the progress of overall debonding is dependent on the species of the broken components and on the geometrical location of broken components and debonded interfaces;and (d) the stress-strain curve shows drops in stress due to the progress of debonding. As an extended application of the present method, a nondimensional Monte Carlo simulation method was presented to describe the behavior of the composite in which the number and location of broken components and debonded interface vary with increasing strain.

A non-dimensional method to increase the accuracy of turbine flowmeters

Turbine flowmeters are inherently non-linear at low flowrates. A computer can, however, correct this non-linearity. The most common method of linearization currently used is based on a graph of the K factor (transducer pulses per litre) against the flowrate. This method is only accurate for the fluid properties for which the meter was calibrated. The accuracy deteriorates substantially if oil of a different viscosity, or the same oil at a different temperature, is used. This paper reports a new method of compensating for changes in viscosity over a large range. Tests on three sizes of flowmeter were carried out, using oil and water. Two dimensionless groups, modifications of the well-known Strouhal and Reynolds numbers, were used to produce plots of the data. The results were shown to compensate for changes in viscosity and also removed some of the underlying dimensional differences between the different turbines. The resulting sixth-order polynomial is used for flowmeters of different sizes, but with a different set of coefficients for each. The final result provides both a more versatile and a more portable method of linearizing turbine flowmeters.

Microscopic and Mesoscopic Evaluations of Materials. Approximate Solution of Interactions among Spacially Distributed Broken Fiber, Matrix and Interface in Progress of Interfacial Debonding in Multifilamentary Unidirectional Composites.

In order to describe the relation of mesoscopic phenomena such as interfacial debonding, and breakage of fiber and matrix to macroscopic stress-strain curve of unidirectional composites, an approximate nondimensional solution method was presented using two-dimensional model. With application of this method to several examples in which the species and locations of broken components were varied to each other, the features that the fiber-breakage-induced debonding occurs at lower strain than the matrix-breakage-induced one, the overall debonding is accelerated due to the mechanical interactions under the existence of many broken fiber and matrix, the progress of overall debonding is dependent on species of the broken components and on the geometrical location of broken components and debonded interface, and stress-strain curve shows drops in stress due to progress of debonding were revealed. Also as an extended application of the present method, a nondimensional Monte Carlo Simulation method was presented to describe the behavior of the composite in which the number and location of broken components and debonded interface vary with increasing strain.

Future large aircraft design — the delta with suction

AbstractSince the 1970s, large passenger aircraft design has evolved by modest, but commercially significant, incremental change following the underwing pod concept pioneered by the Boeing 707. In the 21st century, the market is likely to require greater passenger capacity to deal with air-side congestion and higher performance and operational efficiency to justify investment and conserve finite fossil fuel resources. Public opinion will require far greater emphasis on control of noise and engine exhaust pollution. There is likely to be much increased emphasis on pollution in the upper-atmosphere and its environmental impact. In such a situation, it is questionable whether the evolutionary design route can produce the necessary advances and this must stimulate the search for radical design alternatives.A revolutionary approach, involving the delta planform combined with wing laminar flow control and its impact on overall design, is given a preliminary study in this paper. This has been carried out by assuming that major improvements in drag can be obtained by extensive laminarisation. Using non-dimensional methods, the resulting broad interactive impacts on airframe and engine design and performance are derived. The effect of assuming varying quantities of low-energy air sucked from the foot of the boundary layer is studied and suction-system performance examined.In addition to the large potential improvements in range, a strong relationship between lower drag, lower cruising altitude and lower cruise engine size is identified. In the study, several factors emerge which may combine to drive large aircraft design towards low aspect ratio and the integrated delta wing planform. This paper is intended as a stimulus and a basis for further study and research.

Pile Horizontal Soil Modulus Values

Both nonlinear P-y curves and nondimensional methods for lateral load pile design require the evaluation, measurement, or calculation of a soil horizontal modulus value. Current researchers and foundation design engineers frequently use different notations and procedures that do not make clear the transfer mechanism. This note attempts to clarify the mobilized resistance mechanisms for a laterally loaded pile by considering both side shear and front pressures. No currently popular methods attempt to quantify the contribution of side shear, but it has been shown that side shear is the major contributor to equilibrium at working loads. Any modulus value which expresses the soil reaction as an equivalent uniform pressure across the pile face (diameter) is conservative, if based solely on measured pressures alone.

A Method of Structural Analysis for Small Items in a Random Vibration Environment, Part II

To perform engineering analyses in the most cost-effective manner, engineers must eliminate non-critical design items from a detailed analysis program and concentrate on the marginal and critical design items. This paper shows an approach to accomplishing this objective through the use of a rapid single-degree-of-freedom analysis. Part I develops equations for determining dynamic stresses on structural items modeled as simple beams and presents a non-dimensional method for determining the equivalent spring rate of a variable-stiffness beam. Part II presents a step-by-step example that provides the deflection, equivalent stiffness, frequency and dynamic stress on two different beam configurations with their predicted times-to-failure. In addition, the deflection and frequency results from a finite-elementmodel analysis of two tapered brackets are compared with the results from the non-dimensional variable-stiffness beam method developed previously.

A Method of Structural Analysis For Small Items in A Random Vibration Environment, Part I.

To perform engineering analyses in the most cost-effective manner, engineers must eliminate noncritical design items from a detailed analysis program and concentrate on the marginal and critical design items. This paper shows an approach to accomplishing this objective through the use of a rapid single-degree-of-freedom analysis. Part I develops equations for determining dynamic stresses on structural items modeled as simple beams and presents a nondimensional method for determining the equivalent spring rate of a variable-stiffness beam. Part II presents a step-by-step example that provides the deflection, equivalent stiffness, frequency, and dynamic stress on two different beam configurations with their predicted times-to-failure. In addition, the deflection and frequency results from a finite-element-model analysis of two tapered brackets are compared with the results from the nondimensional variable stiffness beam method developed previously.

A Direct Nondimensional Clustering Method for Binary Data

SUMMARY A new clustering method for binary data is proposed. The method is based on the new concept of homogeneity within a set of two or more operational taxonomic 1lnits. It should entirely replace the previous procedure of calculating a similarity coeHicient, in which the results need to be worked out by a second, logically entirely dilarerent, method of cluster analysis. Homogeneity ill this sense may be considered as a generalized measure of similarity. Moleover, a probability value is associated with every possible cluster and only statistically significant clusters are considered. Probability being a scalar quantity, the method allows two-dimensional graphic representation of the results without loss or distortion of information as in the methods previously proposed. 1. Introductioll A large number of basically similar techniques have been developed in the last 20 years under the name of 'numerical taxonomy'. The purpose of numerical taxonomy can be briefly defined as the construction of objective clusters of units by means of a quantitative measure of their affinity. Its name comes from the fact that the first methods were proposed for, and essentially applied to, the biological classification. However, non-numerical taxonomists still doubt the possibility of producing a purely numericallybased classification if a priori assumptions on the relative primitiveness and Oll the relative values of the characters employed need to be made. We shall not discuss this point here, but we emphasize that numerical taxonomic methods present a very powerful multiple comparison instrument insufficiently known or used in several disciplines, ranging from ecology to archaeology and from biostratigraphy to psychiatry. Sneath and Sokal (1973) give a comprehensive review of the available methods and of their published applications. A numerical taxonomic analysis aims to construct clusters of particularly similar objects among a set of objects to be classified (termed as OTtJs, 'operational taxonomic units'). This is usually done in two different steps. First an L x L symmetric similarity matrix is calculated by means of a similarity coefficient, to measure the similarity between every possible pair among the L OTtJs to be studied. Similarity being homologous to distance, the similarity matrix will occupy an (L- 1)-dimensional hyperspace. For sets including more than a few OTtJs, a similarity matrix obviously becomes hard to read and impossible to understand. For this reason, a second procedure, called cluster analysis, is employed to allow a two-dimensional graphical representation of the

Design Hyetographs for Small Drainage Structures

Improved methods for design and pollution control of storm drainage facilities require not only the average rainfall intensity but also the time distribution of the rainfall. Since the temporal pattern of rainfall varies with storms and the patterns of future storms cannot be predicted exactly, the design hyetograph can only be determined probabilistically using statistical values of past events. The nondimensional triangular hyetograph method is based on the statistical mean of the first time moment of recorded rainstorms and triangular representation of the hyetographs, which are nondimensionalized using the rainfall duration and depth. For a given season the expected nondimensional triangular hyetographs for heavy rainstorms are nearly identical, being insignificantly affected by the duration of rainfall. The established nondimensional triangular hyetograph can then be used to produce the design hyetographs by simple procedures. Results of an analysis of 7,484 rainstorms at three locations indicate that such a method is feasible.