Mathematical modeling and the study of exchange processes in disperse boundary layer control actions

A significant interest of researchers is attracted to the effective management and forecasting of exchange processes in the boundary layer, which are key for the implementation of effective and reliable equipment. Modeling of exchange processes occurring in a high-speed dispersed boundary layer with external influences is a very difficult task. Mathematical modeling allows us to develop reliable devices and engines for the fields of aircraft, energy, shipbuilding with minimal costs for its creation. Despite the interest of numerous groups of researchers around the scientific projects and a large number of works, the current theory of the boundary layer is imperfect. This may be due to several circumstances: firstly, the theory of single-phase turbulent flows of continuous media is far from being completed, secondly, turbulent flows with dispersed impurities in the form of particles greatly complicate the already intricate flow pattern. Interest in dispersed flows is particularly relevant due to the fact that almost all gas-dynamic flows contain a certain concentration of particles, and their impact can provoke significant changes in the structure of the boundary layer and affect the intensity of exchange processes. The article proposes a two-fluid mathematical model describing the motion of a high-speed dispersed boundary layer on a surface with hemispherical damping cavities. The use of hemispherical damping cavities allows to reduce turbulent exchange in the boundary layer, which makes it possible to control the intensity of metabolic processes. The possibility of a significant reduction of turbulent heat transfer and friction in the dispersed boundary layer is established. The proposed method of impact on the turbulent transport in the boundary layer will improve the equipment and installations, including GTU and GTE used in various industries of our country, such as energy, aircraft, shipbuilding.

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Unsteady Flow Structure Behind a Heated Cylinder Measured by Time-Resolved PIV With Thermocouple Sensing

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44499 ◽

2011 ◽

Cited By ~ 1

Author(s):

Yuji Ohta ◽

Takuya Mukoyama ◽

Koichi Hishida

Keyword(s):

Unsteady Flow ◽

Turbulent Flows ◽

Simultaneous Measurement ◽

High Speed ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Wake Region ◽

Time Resolved ◽

Heated Cylinder ◽

Thermal Fluid Flow

This paper deals with a technique for time-resolved simultaneous measurement of velocity and temperature in wake region. A measurement technique, combining a high-speed particle image velocimetry (PIV, 1000 frame per second) with thermo-couple sensing (T-type, 50μm), has been developed for acquiring time-resolved two-dimensional velocity and temperature data in thermal-fluid flow, simultaneously. To accomplish the simultaneous measurement, thermocouple time constant was compensated by solving inverse problem with experimental time-resolved velocity data. The technique was applied to a wake region behind a heated circular cylinder in steady and unsteady flow. The evolutions of vortical and thermal structures were obtained in order to examine the mechanism of the turbulent heat transfer in such turbulent flows.

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INTENSIFICATION OF TURBULENT TRANSPORT IN A BOUNDARY LAYER NEAR THE SURFACE STREAMLINED BY A HIGH-SPEED DISPERSED FLOW

10.1615/ihtc16.cov.024392 ◽

2018 ◽

Author(s):

R. V. Fedorov ◽

Vladislav N. Kovalnogov

Keyword(s):

Boundary Layer ◽

High Speed ◽

Turbulent Transport ◽

Dispersed Flow

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Experiments on Flame Flashback in a Quasi-2D Turbulent Wall Boundary Layer for Premixed Methane-Hydrogen-Air Mixtures

Volume 2: Combustion, Fuels and Emissions, Parts A and B ◽

10.1115/gt2010-23401 ◽

2010 ◽

Cited By ~ 2

Author(s):

Christian Eichler ◽

Thomas Sattelmayer

Keyword(s):

Boundary Layer ◽

Boundary Layers ◽

Turbulent Flows ◽

Turbulent Transport ◽

Wall Friction ◽

Evaluation Procedure ◽

Wall Boundary Layer ◽

Wall Boundary ◽

Flame Flashback ◽

Turbulent Wall

Premixed combustion of hydrogen-rich mixtures involves the risk of flame flashback through wall boundary layers. For laminar flow conditions, the flashback mechanism is well understood and is usually correlated by a critical velocity gradient at the wall. Turbulent transport inside the boundary layer considerably increases the flashback propensity. Only tube burner setups have been investigated in the past and thus turbulent flashback limits were only derived for a fully-developed Blasius wall friction profile. For turbulent flows, details of the flame propagation in proximity to the wall remain unclear. This paper presents results from a new experimental combustion rig, apt for detailed optical investigations of flame flashbacks in a turbulent wall boundary layer developing on a flat plate and being subject to an adjustable pressure gradient. Turbulent flashback limits are derived from the observed flame position inside the measurement section. The fuels investigated cover mixtures of methane, hydrogen and air at various mixing ratios. The associated wall friction distributions are determined by RANS computations of the flow inside the measurement section with fully resolved boundary layers. Consequently, the interaction between flame back pressure and incoming flow is not taken into account explicitly, in accordance with the evaluation procedure used for tube burner experiments. The results are compared to literature values and the critical gradient concept is reviewed in light of the new data.

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Study of turbulent heat transfer enhancement by turbulence promotor placed in turbulent boundary layer.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.55.3485 ◽

1989 ◽

Vol 55 (519) ◽

pp. 3485-3492

Author(s):

Masatomo HORI ◽

Kenji YAMAGUCHI ◽

Junzo YATA ◽

Tatsuo MINAMIYAMA

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Turbulent Boundary Layer ◽

Heat Transfer Enhancement ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Transfer Enhancement

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DNS study on turbulent heat transfer induced by virtual turbulence at inlet in boundary layer on a flat plate

The Proceedings of the Thermal Engineering Conference ◽

10.1299/jsmeted.2020.0125 ◽

2020 ◽

Vol 2020 (0) ◽

pp. 0125

Author(s):

Hirofumi HATTORI ◽

Keita KANO ◽

Haruka TADANO ◽

Tomoya HOURA ◽

Masato TAGAWA

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Flat Plate ◽

Turbulent Heat Transfer ◽

Turbulent Heat

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Control of Turbulent Transport: Less Friction and More Heat Transfer

Journal of Heat Transfer ◽

10.1115/1.4005151 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 14

Author(s):

Nobuhide Kasagi ◽

Yosuke Hasegawa ◽

Koji Fukagata ◽

Kaoru Iwamoto

Keyword(s):

Heat Transfer ◽

Heat Transport ◽

Turbulent Transport ◽

Scalar Fields ◽

Wall Friction ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Control Input ◽

Divergence Free Vector ◽

Wide Range

Because of the importance of fundamental knowledge on turbulent heat transfer for further decreasing entropy production and improving efficiency in various thermofluid systems, we revisit a classical issue whether enhancing heat transfer is possible with skin friction reduced or at least not increased as much as heat transfer. The answer that numerous previous studies suggest is quite pessimistic because the analogy concept of momentum and heat transport holds well in a wide range of flows. Nevertheless, the recent progress in analyzing turbulence mechanics and designing turbulence control offers a chance to develop a scheme for dissimilar momentum and heat transport. By reexamining the governing equations and boundary conditions for convective heat transfer, the basic strategies for achieving dissimilar control in turbulent flow are generally classified into two groups, i.e., one for the averaged quantities and the other for the fluctuating turbulent components. As a result, two different approaches are discussed presently. First, under three typical heating conditions, the contribution of turbulent transport to wall friction and heat transfer is mathematically formulated, and it is shown that the difference in how the local turbulent transport of momentum and that of heat contribute to the friction and heat transfer coefficients is a key to answer whether the dissimilar control is feasible. Such control is likely to be achieved when the weight distributions for the stress and flux in the derived relationships are different. Second, we introduce a more general methodology, i.e., the optimal control theory. The Fréchet differentials obtained clearly show that the responses of velocity and scalar fields to a given control input are quite different due to the fact that the velocity is a divergence-free vector, while the temperature is a conservative scalar. By exploiting this inherent difference, the dissimilar control can be achieved even in flows where the averaged momentum and heat transport equations have the same form.

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Prediction of compressible turbulent boundary layer via a symmetry-based length model

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.710 ◽

2018 ◽

Vol 857 ◽

pp. 449-468 ◽

Cited By ~ 2

Author(s):

Zhen-Su She ◽

Hong-Yue Zou ◽

Meng-Juan Xiao ◽

Xi Chen ◽

Fazle Hussain

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Layer Structure ◽

Analytic Form ◽

Algebraic Model ◽

Length Function ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Reynolds Analogy ◽

The Mean

A recently developed symmetry-based theory is extended to derive an algebraic model for compressible turbulent boundary layers (CTBL) – predicting mean profiles of velocity, temperature and density – valid from incompressible to hypersonic flow regimes, thus achieving a Mach number ($Ma$) invariant description. The theory leads to a multi-layer analytic form of a stress length function which yields a closure of the mean momentum equation. A generalized Reynolds analogy is then employed to predict the turbulent heat transfer. The mean profiles and the friction coefficient are compared with direct numerical simulations of CTBL for a range of$Ma$from 0 (e.g. incompressible) to 6.0 (e.g. hypersonic), with an accuracy notably superior to popular current models such as Baldwin–Lomax and Spalart–Allmaras models. Further analysis shows that the modification is due to an improved eddy viscosity function compared to competing models. The results confirm the validity of our$Ma$-invariant stress length function and suggest the path for developing turbulent boundary layer models which incorporate the multi-layer structure.

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