Modelling air infiltration due to wind fluctuations—a review

Haghighat, Fariborz; Brohus, Henrik; Rao, Jiwu

doi:10.1016/s0360-1323(99)00028-1

Cited by 54 publications

(30 citation statements)

References 7 publications

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“…Haghighat et al [12] indicated that ventilation in buildings due to wind-induced pressure drop is a complex process that is highly influenced by the turbulent nature of the wind, especially when the root mean square of the pressure fluctuations at the building envelop is relatively large compared with the mean wind pressure. Etheridge [9] indicated that as far as is known all current design procedures employed in practice ignore unsteady flow effects due to fluctuating wind pressures in natural ventilation.…”

Section: Introductionmentioning

confidence: 99%

Heat Fluxes and Airflow Patterns Through Roof Windows in a Naturally Ventilated Enclosure

Teitel

Tanny

2005

Flow Turbulence Combust

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Experiments were carried out to study the airflow and heat transfer through continuous vertical roof openings of a naturally ventilated greenhouse. The major goals of this work were to investigate the effect of ambient wind speed and direction with respect to the greenhouse on the mean and turbulent characteristics of the air velocity and heat transfer through openings with and without insect-proof screens. Air velocity and temperature were measured simultaneously at two edges of the opening using one-dimensional sonic anemometers and miniature thermocouples. It is shown that when the wind is not perpendicular to the plane of the openings there are outflow and inflow, at the windward and leeward edges of the openings respectively. A wind blowing from the back of the openings and nearly perpendicular to them reduced the mean air velocity at the two edges but did not change the turbulent velocity much. Over a considerable part of the day the mean and turbulent air velocities scale with the ambient wind; the total heat flux (mean plus turbulent) scales with the product of the ambient wind and temperature while the turbulent heat flux does not. The integral length scale of the inflow was approximately equal to the height of the opening and was larger than that of the outflow. Installing screens on the openings generated smaller scales and increased the spectral decay rate in comparison with openings without screens. A quadrant analysis enabled the determination of the events that significantly contribute to the turbulent heat flux. It is shown that at the outflow the turbulent heat flux is mainly due to eddies of cool air entering from the surrounding to the greenhouse while at the inflow it is due to both warm and cool eddies leaving and entering the greenhouse respectively. Nomenclature C p = specific heat of air, J kg −1 K −1 Co = co-spectra of velocity and temperature fluctuations, m s −1 K E = spectral density function, m 3 s −2 f = frequency, Hz F u = velocity flatness F θ = temperature flatness H = threshold H c = total heat flux, W m −2 L = integral length scale, m r uθ = correlation coefficient between u and θ 22 M. TEITEL AND J. TANNY R (t) = autocorrelation function of velocity S i,H = normalized conditional heat flux S u = velocity skewness S θ = temperature skewness T = temperature, K T 0 = ambient temperature, K u = fluctuating air velocity through the opening, m s −1 u = RMS of velocity, m s −1 U = mean air velocity through the opening, m s −1 U 0 = ambient wind speed, m s −1 U n = normalized mean air velocity through the opening u n = normalized RMS of velocityGreek Symbols θ = temperature fluctuation, K θ = RMS of temperature, K ρ = air density, Kg m −3 T = temperature difference between air at the opening and the ambient, K T a = temperature difference between average greenhouse air and the ambient, K

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Section: Introductionmentioning

confidence: 99%

Heat Fluxes and Airflow Patterns Through Roof Windows in a Naturally Ventilated Enclosure

Teitel

Tanny

2005

Flow Turbulence Combust

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“…These are calculated using empirical equations. Examples of this type can be found in [14], [33], [34] and [35].…”

Section: Large and Very Large Openingsmentioning

confidence: 98%

A perspective on fifty years of natural ventilation research

Etheridge

2015

Building and Environment

133

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“…But the airflow fluctuation may lead to large effective air exchange rate in real case, where the mean value of the fluctuating airflow is still small (even zero). Several past studies have proposed theoretical models to study the influence of airflow fluctuations on ventilation rates (Haghighat et al 2000;Etheridge 2000aEtheridge , 2000b. The main purpose of this paper is to develop a simple but straightforward model to further assess this problem.…”

Section: Introductionmentioning

confidence: 99%

A simple model to study the influence of fluctuating airflow on the effective air exchange rate when using natural ventilation

Zhao

Zeng²

2009

Build. Simul.

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Fluctuating airflow may strongly influence the real air exchange rate when using natural ventilation, resulting in a larger "effective" air exchange rate than the "mean" air exchange rate calculated by conventional methods (i.e., the network method). To study the effective air exchange rate during natural ventilation under conditions of actual use, this study proposes a simple model that accounts for fluctuating airflow. The model assumes that the airflow near a building opening fluctuates regularly and velocity is assumed to have either a square or sine wave pattern. Our analysis shows that the effective air exchange rate is larger when accounting for fluctuating airflow. This suggests that the mean air exchange rate should not be calculated without consideration of real airflow fluctuations.

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Modelling air infiltration due to wind fluctuations—a review

Cited by 54 publications

References 7 publications

Heat Fluxes and Airflow Patterns Through Roof Windows in a Naturally Ventilated Enclosure

Heat Fluxes and Airflow Patterns Through Roof Windows in a Naturally Ventilated Enclosure

A perspective on fifty years of natural ventilation research

A simple model to study the influence of fluctuating airflow on the effective air exchange rate when using natural ventilation

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