| 1. |
- Alfredsson, P. Henrik, et al.
(författare)
-
Flows Over Rotating Disks and Cones
- 2024
-
Ingår i: Annual Review of Fluid Mechanics. - : Annual Reviews. - 0066-4189 .- 1545-4479. ; 56, s. 45-68
-
Forskningsöversikt (refereegranskat)abstract
- Rotating-disk flows were first considered by von Karman in a seminal paper in 1921, where boundary layers in general were discussed and, in two of the nine sections, results for the laminar and turbulent boundary layers over a rotating disk were presented. It was not until in 1955 that flow visualization discovered the existence of stationary cross-flow vortices on the disk prior to the transition to turbulence. The rotating disk can be seen as a special case of rotating cones, and recent research has shown that broad cones behave similarly to disks, whereas sharp cones are susceptible to a different type of instability. Here, we provide a review of the major developments since von Karman's work from 100 years ago, regarding instability, transition, and turbulence in the boundary layers, and we include some analysis not previously published.
|
|
| 2. |
- Bec, J., et al.
(författare)
-
Statistical Models for the Dynamics of Heavy Particles in Turbulence
- 2024
-
Ingår i: ANNUAL REVIEW OF FLUID MECHANICS. - 0066-4189 .- 1545-4479. ; 56, s. 189-213
-
Forskningsöversikt (refereegranskat)abstract
- When very small particles are suspended in a fluid in motion, they tend to follow the flow. How such tracer particles are mixed, transported, and dispersed by turbulent flow has been successfully described by statistical models. Heavy particles, with mass densities larger than that of the carrying fluid, can detach from the flow. This results in preferential sampling, small-scale fractal clustering, and large relative velocities. To describe these effects of particle inertia, one must consider both particle positions and velocities in phase space. In recent years, statistical phase-space models have significantly contributed to our understanding of inertial-particle dynamics in turbulence. These models help to identify the key mechanisms and nondimensional parameters governing the particle dynamics and have made qualitative and, in some cases, quantitative predictions. This article reviews statistical phase-space models for the dynamics of small, yet heavy, spherical particles in turbulence. We evaluate their effectiveness by comparing their predictions with results from numerical simulations and laboratory experiments, and we summarize their successes and failures.
|
|
| 3. |
- Brandt, Luca, et al.
(författare)
-
Particle-Laden Turbulence : Progress and Perspectives
- 2022
-
Ingår i: Annual Review of Fluid Mechanics. - : Annual Reviews. - 0066-4189 .- 1545-4479. ; 54, s. 159-189
-
Forskningsöversikt (refereegranskat)abstract
- This review is motivated by the fast progress in our understanding of the physics of particle-laden turbulence in the last decade, partly due to the tremendous advances of measurement and simulation capabilities. The focus is on spherical particles in homogeneous and canonical wall-bounded flows. The analysis of recent data indicates that conclusions drawn in zero gravity should not be extrapolated outside of this condition, and that the particle response time alone cannot completely define the dynamics of finite-size particles. Several breakthroughs have been reported, mostly separately, on the dynamics and turbulence modifications of small inertial particles in dilute conditions and of large weakly buoyant spheres. Measurements at higher concentrations, simulations fully resolving smaller particles, and theoretical tools accounting for both phases are needed to bridge this gap and allow for the exploration of the fluid dynamics of suspensions, from laminar rheology and granular media to particulate turbulence.
|
|
| 4. |
- Lesser, Martin B., et al.
(författare)
-
The impact of compressible liquids
- 1983
-
Ingår i: Annual Review of Fluid Mechanics. - : Annual Reviews. - 0066-4189 .- 1545-4479. ; 15, s. 97-122
-
Tidskriftsartikel (refereegranskat)abstract
- Consideration is given to liquid impact in the supersonic regime in order to characterize pressure loading and other mechanisms which could damage a solid target such as a jet in flight. The liquid mass is treated as having a free surface, while the solid is assumed linear elastic. During contact, the fluid is maintained as a continuum and the solid becomes a homogeneous and isotropic elastic material. The processes have been described analytically and numerically by incompressible models, by water entry models, and with two-dimensional calculations. Experimentation has been performed with single and multiple impact techniques, with attention given to jetting, the jetting angle, impact pressures, and impacts on a wetted surface. High edge pressures have been observed, as has cavitation in the liquid and detachment of the edge shock. The presence of a liquid film on the surface of the object has been found to significantly affect the extent of erosion.
|
|
| 5. |
- Lundell, Fredrik, et al.
(författare)
-
Fluid Mechanics of Papermaking
- 2011
-
Ingår i: Annual Review of Fluid Mechanics. - : Annual Reviews. - 0066-4189 .- 1545-4479. ; 43, s. 195-217
-
Forskningsöversikt (refereegranskat)abstract
- Papermaking is to a large extent a multiphase flow process in which the structure of the material and many of the relevant properties of the final product are determined by the interaction between water and the wood fibers. The dominant feature of a suspension composed of wood fibers and water is its inherent propensity to form bundles of mechanically entangled fibers, known as fiber flocs. However, the phenomena apparent throughout the papermaking process are not unique but in fact have a generic fluid dynamical nature.
|
|
| 6. |
- Sabelnikov, Vladimir, 1946, et al.
(författare)
-
Recent advances in understanding of thermal expansion effects in premixed turbulent flames
- 2017
-
Ingår i: Annual Review of Fluid Mechanics. - : Annual Reviews. - 1545-4479 .- 0066-4189. ; 49, s. 91-117
-
Forskningsöversikt (refereegranskat)abstract
- When a premixed flame propagates in a turbulent flow, not only does turbulence affect the burning rate (e.g., by wrinkling the flame and increasing its surface area), but also the heat release in the flame perturbs the pressurefield, and these pressure perturbations affect the turbulent flow and scalar transport. For instance, the latter effects manifest themselves in the so-calledcountergradient turbulent scalar flux, which has been documented in various flames and has challenged the combustion community for approximately 35 years. Over the past decade, substantial progress has been made in investigating (a) the influence of thermal expansion in a premixed flame on the turbulent flow and turbulent scalar transport within the flame brush, as well as (b) the feedback influence of countergradient scalar transport on the turbulent burning rate. The present article reviews recent developments in this field and outlines issues to be solved in future research.
|
|
