While natural convection in rectangular boxes has been studied extensively, the flow inside cylindrical enclosures is less understood but equally important for applications like hydrocarbon storage tanks. This report details a Laminar Natural Convection CFD simulation inside a vertical cylinder. The primary goal is to perform a detailed Laminar Natural Convection VALIDATION CFD by comparing our results against the benchmark data from the paper, “Laminar natural convection in a laterally heated and upper cooled vertical cylindrical enclosure” [1].

• Reference [1]: Lemembre, A., and J-P. Petit. “Laminar natural convection in a laterally heated and upper cooled vertical cylindrical enclosure.” International journal of heat and mass transfer16 (1998): 2437-2454.

Figure 1: The vertical cross-section of the cylindrical enclosure geometry from the reference study [1].

Simulation Process: Modeling the Natural Convection Fluent Simulation

The simulation was performed on a 2D geometry representing a vertical slice of the cylinder, as shown in Figure 1. This is possible because the flow is assumed to be axisymmetric (symmetrical around the central axis). The flow is laminar, and the simulation uses the Boussinesq approximation. This is a standard and accurate method for natural convection problems, which assumes that the density of the air changes only with temperature and only in the gravity term, which is what drives the flow. All calculations for this Natural Convection In Cylindrical Enclosure Fluent simulation were performed using ANSYS Fluent.

Post-processing: CFD Analysis, Validating the Model and Understanding the Flow

The simulation results provide a clear and fully substantiated story that begins with proving our model is accurate. The primary “cause” of the flow is the boundary conditions: the side walls are heated, and the top wall is cooled. This setup creates density differences in the air. The “effect” is a specific temperature distribution. Figure 2 shows a plot of the vertical temperature profile near the bottom of the cylinder. Our CFD simulation results (the colored circles) align almost perfectly with the results from the reference paper (the black line). This excellent agreement is the core of our Laminar Natural Convection VALIDATION CFD; it proves that our simulation setup, including the mesh and the Boussinesq approximation, is correctly capturing the real-world physics for this specific problem (Rayleigh number Ra=10^5, Prandtl number Pr=0.7).

Figure 2: The validation plot showing excellent agreement between the current CFD simulation and the reference paper [1] for the temperature profile.

With our model now validated and trusted, we can analyze the detailed physics it reveals. The velocity contour in Figure 3 is the visual proof of the flow structure. The air heated by the side walls becomes lighter and rises. When it reaches the top, the cold surface cools it down, making it heavier. This heavier air then sinks down the center of the cylinder. This process creates a fascinating and elegant flow pattern of two large, counter-rotating vortices, with the highest velocity (red) occurring where the cool air sinks down the middle. This is a unique feature of this cylindrical geometry and heating arrangement. The temperature contour confirms this story, showing warm regions (orange-red) near the side walls and a distinct plume of cool fluid (blue-green) being pushed down the center by the descending flow. The most significant achievement of this study is the successful validation against benchmark data, which gives us high confidence that our CFD model accurately captures the unique twin-vortex circulation pattern (the effect) that is driven by the specific thermal boundary conditions (the cause) in a cylindrical enclosure.

Figure 3: Velocity and Temperature fields from the Natural Convection In Cylindrical Enclosure CFD simulation, showing the twin-vortex structure and thermal stratification.