|
|
Numerická simulace Kármánovy vírové řady
Šponiar, D. ; Trávníček, Zdeněk ; Vogel, Jiří
The wake airflow behind a circular cylinder has been investigated using FLUENT solver. The flow is assumed to be two–dimensional, laminar, isothermal, and incompressible. The Reynolds number ranges Re = 30:-170. The computations give the steady wake flow for Re = 30:-60 and the periodic vortex shedding (von Kármán vortex street) for Re = 60:-170. The vortex shedding frequency has been quantified in the term of the Strouhal number–Reynolds number relationship. The present results agree very well with the previous experimental data, the maximum deviations of the simulations and experiments are within 1.2%.
|
|
|
Experimentální mechanika tekutin a sdílení tepla a hmoty: strategie výzkumu
Trávníček, Zdeněk
The so-called “Research Strategy” seems to be a typical and quite effective tool for dealing with various problems in Experimental Thermal Fluid Sciences. The working hypothesis is proposed first and then a specific plan is derived from the hypothesis. The problem is divided into manageable parts (step-by-step approach). The purpose of the experiments is to confirm or to reject the hypothesis. The presentation introduces several examples of the recent original results: the influence of the flow structure on heat transfer, passive/active flow control of impinging jets, convective heat transfer enhancement of (steady or pulsatile) impinging jets, synthetic jets, hybrid synthetic jets, stability and bistability of jets, and thermal flow control of wakes. The examples emphasize the role of the discussed methodology, namely the roles of the task motivation, working hypothesis, and interpretation and publication of the results.
|
|
|
Analysis of the synthetic jet at the actuator output
Kordík, J. ; Šafařík, P. ; Vít, T. ; Trávníček, Zdeněk
The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation.The paper focuses on a pulsatile axisymmetric flow in an outlet orifice of a zero-net-mass-flux actuator of a synthetic air jet. A simplified task (pulsatile pipe flow) is studied theoretically. Velocity profiles have been measured using hot-wire anemometry; the approximation of the experimental data is based on the theoretical solution. The results improve our knowledge of synthetic jets and provide data for their advanced numerical simulation.
|
|
| |
|
|
Přestup tepla a hmoty u syntetizovaného impaktního proudu
Trávníček, Zdeněk ; Hyhlík, Tomáš ; Maršík, František
A zero–net–mass–flux actuator was used to generate a synthetic air jet. The local mass transfer in the jet impingement configuration was investigated using the naphthalene sublimation method. Based on the heat/mass transfer analogy, the mass transfer data have been converted to the corresponding heat transfer data. The results have been compared with the data for continuous impinging jets; the difference is less than 11%.
|
|
|
Numerická simulace a vizualizace vytváření syntetizovaného proudu
Trávníček, Zdeněk ; Vogel, Jiří ; Vít, T.
The paper presents the results of numerical and experimental investigations of a synthetic jet generation. The experiments were performed in air by means of flow visualization and hot-wire anemometry. The subsequent numerical simulation was performed using the commercial code FLUENT. The geometry, boundary conditions, and material properties of the numerical simulation were defined according to the real experimental situation.
|
|
|
Numerické řešení sdílení tepla v proudu dopadajícím na stěnu
Kozel, K. ; Louda, Petr ; Příhoda, Jaromír
The paper deals with the numerical solution of 3D impinging turbulent jet cooling a weakly heated wall. The solution was carried out using the SST model and/or an explicit algebraic Reynolds stress model and completed by a generalized gradient-diffusion hypothesis for modelling of turbulent heat flux. While the EARSM model gives good results for the velocity field, all used models overestimate heat transfer in the impingement region.
|
|
|
Numerické modelování složitých turbulentních proudění
Kozel, K. ; Louda, Petr ; Příhoda, Jaromír
The work deals with the numerical solution of turbulent impinging jet and round jet in a cross flow. The mathematical model is based on averaged Navier-Stokes equations closed by a turbulence model. Turbulence models used are a low-Reynolds-number eddy-viscosity model and/or an explicit algebraic Reynolds stress model. Numerical results are compared with experimental data. In case of impinging jet flow, the heat transfer is also solved.
|
guest ::
