CFD Simulation for Thermal Comfort in High-Rise Towers in the Gulf (KSA, Oman, Kuwait)

Abstract

High-rise towers in the Gulf face a unique thermal challenge: extreme solar loads, high ambient temperatures, and in many coastal locations, high humidity. Computational Fluid Dynamics (CFD) has become an essential tool to understand indoor airflow, heat transfer and to design HVAC and façade strategies that deliver thermal comfort while minimizing energy use. This blog explains why CFD matters for towers in KSA, Oman and Kuwait, the practical simulation approach, common pitfalls, and actionable design recommendations informed by CFD.

Why CFD for Gulf high-rises?

The Gulf climate combines intense solar radiation, long hot seasons, and local wind patterns (sea breezes, desert winds). In high-rise buildings, these external drivers interact with complex internal geometries (atriums, double-height lobbies, stack-effect shafts, mixed-use floors), making thermal and airflow behavior non-intuitive:

• Nonlinear interactions between façade solar gains, glazing, shading, and internal heat sources.

• Stack effect that can induce vertical airflow (and thermal stratification) in tall shafts.

• Localized discomfort zones (near façades, balconies, or in atrium corners) that are invisible to simple calculations.

• Optimization needs: balancing occupant comfort with energy use (smarter HVAC zoning, natural ventilation strategies, façade tuning).

  
  

CFD lets designers see airflow and temperature fields, test multiple scenarios (orientation, glazing type, AHU strategy), and quantify comfort metrics before construction.

What to simulate (key objectives)

A typical CFD study for thermal comfort in a Gulf high-rise focuses on:

1. Indoor airflow and temperature distribution — detect hotspots, drafts, and dead zones.

2. Thermal stratification and stack effect across vertical shafts and atria.

3. Effectiveness of natural ventilation (where feasible) vs. mechanical ventilation.

4. Façade and glazing impact — Solar heat gains, inward long-wave exchanges, and convection at the façade.

5. Local thermal comfort indices — Predicted Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD), and local airflow velocities.

6. Transient response — diurnal cycles (day/night), occupancy schedules, and HVAC on/off patterns.

7. HVAC supply strategy evaluation — diffuser placement, supply temperature, and air change rates.

   
   

Practical CFD methodology — step by step

1. Define boundary conditions realistically

• Outdoor climate inputs: Typical summer peak and representative diurnal profiles (outdoor temperature, relative humidity, wind speed/direction). For Gulf cases include high solar irradiance and possible sea breeze cycles.

• Façade loads: Solar heat gain through glazing (use SHGC and orientation-based incident radiation), wall conduction.

• Internal loads: Occupancy, lighting, equipment — use realistic schedules.

• HVAC outlets: Diffuser geometry, flow rates, supply temperatures, and control logic.

  
  

2. Geometry and domain

• Model the zones of interest in sufficient detail: occupied spaces, corridors, shafts, double-height atria, balconies, and a simplified exterior domain if wind-driven ventilation is evaluated. Avoid over-simplifying supply diffusers or critical openings.

  
  

3. Mesh strategy

• Use structured or hybrid meshes with refinement near walls, openings, diffusers, and glazing.

• Resolve boundary layers — wall y+ appropriate for chosen turbulence model.

• For atria and shafts where buoyancy dominates, ensure vertical resolution captures thermal gradients.

  
  

4. Physics models & solver choices

• Buoyancy  — essential for stack effect and stratification.

• Turbulence: steady RANS (k-ε or k-ω SST) for design iterations; LES or hybrid RANS-LES for detailed transient comfort/draft studies where small-scale turbulence matters.

• Radiation: include solar/longwave radiation (Discrete Ordinates, DO, or radiosity + view factors) — solar load is a major driver in the Gulf.

• Conjugate heat transfer (CHT): if façade conduction or thermal storage in walls affects indoor temps, couple fluid and solid.

• Humidity modelling: if condensation risk or latent loads matter, include species transport (water vapor) and psychometrics to compute comfort (especially in coastal Kuwait/Oman regions).

• Transient vs steady: run transient simulations for diurnal cycles, start-up events, or naturally ventilated scenarios; steady RANS is fine for many comparative studies.

  
  

5. Comfort metrics & post-processing

• Compute PMV/PPD, airflow velocity maps, operative temperature, and exposure durations outside comfort envelopes.

• Identify vertical temperature gradients (for occupant stratification) and areas exceeding acceptable local velocities (drafts).

• Use visualization: streamlines, isosurfaces, contour slices, and time series at critical points.

  
  

Example project scenarios (illustrative)

1. Façade retrofit for solar control (south-facing high-rise in Riyadh): CFD used to test different shading devices and double-skin façade gap ventilation. Outcome: certain overhang geometries reduced peak cooling load and reduced localized radiant asymmetry near windows.

2. Atrium stack effect in a mixed-use tower (Muscat): Transient CFD showed strong upward flow during daytime, causing warm air to enter upper office levels; introducing controlled exhaust at intermediate floors and automated dampers reduced stratification and improved PMV by ~0.4 on average.

3. Cross-ventilation validation for mid-height floors (Kuwait City): CFD with external wind field coupling verified that sea breeze could drive beneficial cross-ventilation during evening hours; however, daytime high temperatures required blending with mechanical cooling to maintain comfort.