Transverse Vibrations of a Cylinder Very Close to a Plane Wall

1987 ◽  
Vol 109 (1) ◽  
pp. 52-60 ◽  
Author(s):  
J. Fredso̸e ◽  
B. M. Sumer ◽  
J. Andersen ◽  
E. A. Hansen
Keyword(s):  
Mathematical Model ◽  
Lift Force ◽  
Important Influence ◽  
Plane Wall ◽  
Spring Stiffness ◽  
Transverse Vibrations ◽  
Steady Current ◽  
Series Of Experiments

The paper presents a series of experiments carried out with a cylinder suspended by springs and placed very close to a plane wall. The cylinder is exposed to a steady current. The range of gap ratios between zero and one has been studied in detail. Different combinations of spring stiffness and mass of cylinder is applied in the range of reduced velocity between 2 and 10. The proximity of the wall is shown to have important influence on the behavior of the pipe. Some of these trends are explained by a mathematical model including the effect of lift force close to the wall.

scholarly journals MODELING AND PRODUCTIVITY PREDICTION OF THE COMPANIES-INTERNAL CROWDSOURCING-BASED IDEATION

2021 ◽  
Vol 1 ◽  
pp. 2147-2156
Author(s):  
Pavel Livotov
Keyword(s):  
Mathematical Model ◽  
Finite Number ◽  
Research Question ◽  
Performance Function ◽  
Non Linear ◽  
Series Of Experiments ◽  
Productivity Prediction ◽  
A Company

AbstractThe internal crowdsourcing-based ideation within a company can be defined as an involvement of its staff, specialists, managers, and other employees, to propose solution ideas for a pre-defined problem. This paper addresses a question, how many participants of the company-internal ideation process are required to nearly reach the ideation limit for the problems with a finite number of workable solutions. To answer the research question, the author proposes a set of metrics and a non-linear ideation performance function with a positive decreasing slope and ideation limit for the closed-ended problems. Three series of experiments helped to explore relationships between the metric attributes and resulted in a mathematical model which allows companies to predict the productivity metrics of their crowdsourcing ideation activities such as quantity of different ideas and ideation limit as a function of the number of contributors, their average personal creativity and ideation efficiency of a contributors’ group.

Improving Seaplane Seakeeping through the Use of Amortized Floats

2015 ◽  
Author(s):  
Anton N. Varyukhin ◽  
Vladimir V. Veselov ◽  
Maxim A. Ovdienko ◽  
Alexandr V. Arilin ◽  
Sergey V. Dikiy
Keyword(s):  
Mathematical Model ◽  
Important Task ◽  
Series Of Experiments

Seaworthiness characteristics are one of the key conditions for the success of the seaplane. So the improvement of these characteristics is an important task. It was suggested that the using of amortized floats could improve the seaworthiness characteristics of seaplane. For this purpose series of experiments were carried out and mathematical model was developed.

Interaction Between Two Closely Spaced Azimuthing Thrusters

1998 ◽  
Vol 42 (01) ◽  
pp. 15-32 ◽  
Author(s):  
Paul Brandner ◽  
Martin Renilson
Keyword(s):  
Mathematical Model ◽  
Satisfactory Agreement ◽  
Vehicle Dynamics ◽  
Operating Conditions ◽  
Towing Tank ◽  
Empirical Relations ◽  
Series Of Experiments ◽  
Flow Effects ◽  
Semi Empirical

To assist in predicting the performance of omni-directional propelled vehicles a series of experiments has been conducted to measure the interaction between two closely spaced ductedazimuthing thrusters. The thrusters were tested below a shallow draft ground board in a towing tank at a spacing of approximately 2 propeller diameters. Measurements were made of forces acting on a single thruster for a range of operating conditions and similarly on two thrusters for a range of relative positions. The results show that forces from the trailing thruster are heavily affected by interaction, particularly due to impingement of the race from the leading thruster, where as forces from the leading thruster remain essentially unaffected despite its proximity to the trailing thruster. A semi-empirical mathematical model suitable for simulation of omni-directional vehicle dynamics is presented. The model is based on the trajectory of the race from the leading thruster derived from momentum considerations with additional empirical relations to account for other more minor flow effects. Comparison of the predicted and measured results show satisfactory agreement.

Simulation of fuel bed ignition by wildland firebrands

2018 ◽  
Vol 27 (8) ◽  
pp. 550 ◽  
Author(s):  
O. V. Matvienko ◽  
D. P. Kasymov ◽  
A. I. Filkov ◽  
O. I. Daneyko ◽  
D. A. Gorbatov
Keyword(s):  
Mathematical Model ◽  
Pinus Sylvestris ◽  
Mathematical Modelling ◽  
Thermal Energy ◽  
Ignition Time ◽  
Pine Bark ◽  
Bark Sample ◽  
Airflow Velocity ◽  
Experimental Conditions ◽  
Series Of Experiments

A 3-D mathematical model of fuel bed (FB) ignition initiated by glowing firebrands originating during wildland fires is proposed. In order to test and verify the model, a series of experiments was conducted to determine the FB ignition time by a single pine bark and twig firebrand (Pinus sylvestris). Irrespective of the pine bark sample sizes and experimental conditions, the ignition of the FB was not observed. Conversely, pine twigs, under certain parameters, ignited the FB in the range of densities (60–105 kg m−3) and with the airflow velocity of ≥2 m s−1. The results of the mathematical modelling have shown that a single pine bark firebrand ≤5 cm long with a temperature of T ≤ 1073 K does not ignite in the flaming mode the FB, and only the thermal energy of larger particles is sufficient for flaming ignition of the adjacent layers of the FB. The analysis of the results has shown that the firebrand length is a major factor in the initiation of ignition. Comparison of the calculated and observed FB ignition times by a single firebrand have shown that our modelling accords well with the experimental results.

A new model to predict the behaviour of cavitated squeeze-film bearings

1987 ◽  
Vol 411 (1841) ◽  
pp. 445-466
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Lift Force ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Successful Operation ◽  
New Model ◽  
Damping Coefficients ◽  
Stiffness Coefficients ◽  
Linear Damping

Squeeze-film bearings are used extensively to control vibration in rotor-bearing systems. No closed-form mathematical model exists to represent the stiffness and dam ping characteristics of a cavitated squeeze-film bearing when it is describing a non-circular, non-concentric orbit. In this paper nonlinear expressions are developed for the oil-film forces from which are derived two direct linear stiffness and two direct linear damping coefficients with all the cross stiffness and dam ping coefficients zero. The linearized stiffness coefficients and the damping coefficients are functions of the amplitude of the journal orbit. The dynamic lift-force which is fundamental to the successful operation of a cavitated squeeze-film bearing when designed without centralizing springs has not previously been predicted analytically. An expression is derived for this lift force. Its magnitude is shown to be dependent upon the amplitude of the steady-state orbit, that is, it is dependent upon the dynamic load. A numerical experiment is performed to assess the validity of the new model over a range of operating conditions.

Current transport for a spatially periodic potential system with color noises

2018 ◽  
Vol 32 (31) ◽  
pp. 1850352
Author(s):  
Lijuan Ning ◽  
Jie Wang
Keyword(s):  
Mathematical Model ◽  
External Force ◽  
Periodic Potential ◽  
Current Transport ◽  
Absolute Value ◽  
Steady Current ◽  
Large Current ◽  
Potential System ◽  
Spatially Periodic ◽  
Current Value

The transport of an underdamped particle driven by an external force in a periodic asymmetric potential with color noises is investigated. The corresponding mathematical model is established. By the method of the numerical simulation, we present the movement of the steady current of underdamped particles. Different parameters have different influences on current transport, such as increasing or decreasing. It is shown that the cooperations among the external force and the noises parameter lead to the phenomena: when the external force is not zero, the large external force may cause the large current value or the absolute value of the current. The current value is due to the effect of the cooperations of external force and noise parameter.

Transverse Vibrations of an Elastically Mounted Cylinder Exposed to an Oscillating Flow

1988 ◽  
Vol 110 (4) ◽  
pp. 387-394 ◽  
Author(s):  
B. M. Sumer ◽  
J. Fredso̸e
Keyword(s):  
Oscillatory Flow ◽  
Oscillating Flow ◽  
Response Patterns ◽  
Test Program ◽  
Current Case ◽  
Number Range ◽  
Response Characteristics ◽  
Vibrational Response ◽  
Transverse Vibrations ◽  
Steady Current

This study reports the results of an experimental work carried out with an elastically mounted rigid cylinder exposed to an oscillating flow. To facilitate comparison, the steady current case is included in the test program as well. The oscillatory flow as well as the steady current conditions are created by the so-called carriage technique. The present study covers the Keulegan-Carpenter number range 5 ≤ KC ≤ 100. The range of the reduced velocity is from 0 to approximately 16 in most of the cases. The tests have been conducted for different combinations of spring stiffness and mass of cylinder. The present results shed considerable light into the understanding of the various vibrational response patterns obtained for different ranges of KC number. The response characteristics of the cylinder have been shown to vary extensively, depending on Keulegan-Carpenter number as well as on the reduced velocity.

Railway carriage simulation model to study the influence of vertical secondary suspension stiffness on ride comfort of railway carbody

2011 ◽  
Vol 225 (6) ◽  
pp. 1349-1359 ◽  
Author(s):  
K H A Abood ◽  
R A Khan
Keyword(s):  
Mathematical Model ◽  
Dynamic Response ◽  
Simulation Model ◽  
Lateral Displacement ◽  
Vertical Displacement ◽  
Roll Angle ◽  
Spring Stiffness ◽  
Passenger Comfort ◽  
Secondary Suspension ◽  
Yaw Angle

A mathematical model of a railway carriage moving on tangent tracks is constructed by deriving the equations of motion concern the model in which single-point and two-point wheel–rail contacts are considered. The presented railway carriage model comprises front and rear simple conventional bogies with two leading and trailing wheelsets attached to each bogie. The railway carriage is modeled using 31 degrees of freedom which govern vertical displacement, lateral displacement, roll angle, and yaw angle dynamic response of wheelset, whereas vertical displacement, lateral displacement, roll angle, pitch angle, and yaw angle dynamic response carbody and each of the two bogies were also studied. Linear stiffness and damping parameters of longitudinal, lateral, and vertical primary and secondary suspensions are provided to the railway carriage model. Combination of linear Kalker’s theory and non-linear Heuristic model is adopted to calculate the creep forces introduced at wheel and rail contact patch area. Computer-aided simulation is constructed to solve the governing differential equations of the mathematical model using Runge–Kutta fourth-order method. Principle of limit cycle and phase plane approach is applied to realize the stability and evaluate the concerning critical hunting velocity at which the railway carriage starts to hunt. The numerical simulation model is used to study the influence of vertical secondary suspension spring stiffness on the ride passenger comfort of railway carbody at speeds below and at critical hunting velocity. High magnitudes of vertical secondary spring stiffness suspension introduce undesirable roll and yaw dynamic responses in which affect ride passenger comfort at critical hunting velocity.

Experimental Study on Double-Piston Gas Prover

2013 ◽  
Vol 457-458 ◽  
pp. 560-565
Author(s):  
Hui Yun Chen ◽  
Jia Cheng ◽  
Zhen Wei Huang ◽  
Wen Xin Shen
Keyword(s):  
Mathematical Model ◽  
Experimental Study ◽  
Constant Speed ◽  
Piston Cylinder ◽  
Series Of Experiments

Existing piston gas provers use a single piston cylinder as standard which replace the standard flow of gas by the piston moving at a constant speed. In order to solve the problem that the piston proverflow ceiling is limited by the volume of piston cylinder, we have developed a double-piston gas prover. Firstly, the article introduces the devices principle and mathematical model simply. Then it presents a series of experiments and experiments results of the device. Finally,the paper analyzes the uncertainty of the equipment. The results show that the double-piston gas prover is available.

Predictions of ice-cover development in streams and its effect on dissolved oxygen modelling

1979 ◽  
Vol 6 (2) ◽  
pp. 197-207 ◽  
Author(s):  
E. McBean ◽  
G. Farquhar ◽  
N. Kouwen ◽  
O. Dubek
Keyword(s):  
Mathematical Model ◽  
Water Quality ◽  
Dissolved Oxygen ◽  
Prediction Model ◽  
Data Input ◽  
Quality Model ◽  
Two Stage ◽  
Second Stage ◽  
Series Of Experiments ◽  
Ice Edge

A two-stage mathematical model is developed for predicting dissolved oxygen levels in ice-covered rivers. The first stage of the model is a prediction model for ice-edge progression as a function of time, and the second stage consists of an extrapolation of a widely used 'summer condition' water-quality model. The results of a series of experiments, both field and laboratory-based, which served as data input generators and calibration testing of the model, are provided.Briefcase-study applications of elements of the model to the Speed River and to the Saint John River are included.

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