7/14/2023 0 Comments Turbulent flow vs laminar flow![]() ![]() Understanding the Turbulent Energy Cascade ![]() A better understanding of the turbulent flow regime can be reached by looking at a turbulent energy cascade. Turbulence also differs from laminar flow in that the Reynolds number is significantly higher, as illustrated in the figure above. Turbulent flow regimes are marked by various fluid current changes or eddies, which vary in size as well as direction. laminar flow (Image from Thermal Engineering) Chaotic changes in fluid properties such as temperature and pressure.turbulent flow regimes (which can be distinguished by streamline activity).įor the last classification, laminar flow is characterized by parallel streamlines and well-defined layers, while turbulent flow regimes have the following attributes: multi-phase flow regimes (based on the transitions of the flow), and laminar vs. Examples include internal versus external flow regimes (based on the area or surface that bounds the flow), single-phase vs. In order to explain what a turbulent flow regime is, it is first necessary to define a fluid flow regime.įlow regime refers to the classification of fluid flow according to a definable set of criteria, typically to clearly differentiate between two different flows. Therefore, for system design, it is important to understand and analyze the turbulent flow regime, as this is the area in which these changes occur. The latter is highly undesirable, as turbulence can present problems such as increased drag for aircraft. The Seebeck effect, where a temperature differential will introduce an electrical potential difference that can be utilized to generate current, illustrates this.įor fluid flow, there is a similar conversion from stability to chaos that occurs when changing from laminar to turbulent flow. These dire predictions of the future are misplaced, as total energy is always constant and heat can be reconverted to usable energy. An example of this is the heat generated by electrical current flow that is not available for work at the load. This physical reality has led to notions that the world is consistently moving toward chaos, as many processes release or lose energy as heat. Although entropy represents the amount of unusable thermal energy that cannot be converted into mechanical work, increasing entropy is often taken to mean movement from a more stable to a more unpredictable, random, or chaotic state. ![]() Turbulence causes pressure drop or drag increase, enhances heat transfer, and homogenizes the mixing of fluid/species.Īccording to the Second Law of Thermodynamics, the entropy of a system always increases, provided the process causing the change is irreversible. A transfer of energy occurs between the mean flow and eddies of varying time and length scales, illustrated by the Kolmogorov turbulent energy cascade.įor most applications, the smaller details of turbulence are not important-what matters is the effect of turbulence on the main flow. ![]()
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