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Claesson, Leif
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Publications (10 of 17) Show all publications
Claesson, L. (2018). Kartläggning av vindförhållanden på Gävle Strand: Modellprov utförda i vindtunnel vid Akademin för Teknik och Miljö, Högskolan i Gävle.
Open this publication in new window or tab >>Kartläggning av vindförhållanden på Gävle Strand: Modellprov utförda i vindtunnel vid Akademin för Teknik och Miljö, Högskolan i Gävle
2018 (Swedish)Report (Other academic)
Publisher
p. 11
Series
Working paper, ISSN 1403-8757 ; 57
Keywords
vindförhållanden, vindtunnel, bostadsområde, Gävle, Gävle strand, stadsdelsplanering, vindpåverkan
National Category
Civil Engineering
Identifiers
urn:nbn:se:hig:diva-26068 (URN)
Available from: 2018-01-26 Created: 2018-01-26 Last updated: 2018-05-18Bibliographically approved
Chen, L., Hang, J., Sandberg, M., Claesson, L., Di Sabatino, S. & Wigö, H. (2017). The impacts of building height variations and building packing densities on flow adjustment and city breathability in idealized urban models. Building and Environment, 118, 344-361
Open this publication in new window or tab >>The impacts of building height variations and building packing densities on flow adjustment and city breathability in idealized urban models
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2017 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 118, p. 344-361Article in journal (Refereed) Published
Abstract [en]

Improving city breathability has been confirmed as one feasible measure to improve pollutant dilution in the urban canopy layer (UCL). Building height variability enhances vertical mixing, but its impacts remain not completely explored. Therefore, both wind tunnel experiments and computational fluid dynamic (CFD) simulations are used to investigate the effect of building height variations (six height standard deviations σH = 0%–77.8%) associated to building packing densities namely λp/λf = 0.25/0.375 (medium-density) and 0.44/0.67 (compact) on city breathability. Two bulk variables (i.e. the in-canopy velocity (UC) and exchange velocity (UE)) are adopted to quantify the horizontal and vertical city breathability respectively, which are normalized by the reference velocity (Uref) in the free flow, typically set at z = 2.5H0 where H0 is the mean building height. Both flow quantities and city breathability experience a flow adjustment process, then reach a balance. The adjustment distance is at least three times longer than four rows documented in previous literature. The medium-density arrays experience much larger UC and UE than the compact ones. UE is found mainly induced by vertical turbulent fluxes, instead of vertical mean flows. In height-variation cases, taller buildings experience larger drag force and city breathability than lower buildings and those in uniform-height cases. For medium-density and compact models with uniform height, the balanced UC/Uref are 0.124 and 0.105 respectively, moreover the balanced UE/Uref are 0.0078 and 0.0065. In contrast, the average UC/Uref in height-variation cases are larger (115.3%–139.5% and 125.7%–141.9% of uniform-height cases) but UE/Uref are smaller (74.4%–79.5% and 61.5%–86.2% of uniform-height cases) for medium-density and compact models. 

Keywords
Building height variation, City breathability, Computational fluid dynamics (CFD) simulation, Exchange velocity, Flow adjustment, Wind tunnel, Buildings, Drag, Fluid dynamics, Velocity, Wind tunnels, Building height variations, Computational fluid dynamics simulations, Computational fluid dynamics
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:hig:diva-24214 (URN)10.1016/j.buildenv.2017.03.042 (DOI)000401374600026 ()2-s2.0-85017542097 (Scopus ID)
Note

Funding agencies:

National Natural Science Foundation of China Grant no: 51478486 and 41622502

National Science Fund for Distinguished Young Scholars Grant no: 41425020 

Fundamental Research Funds for the Central Universities Grant no: 161gzd01

Science and Technology program of Guangzhou, China Grant no:  201607010066 

Available from: 2017-06-14 Created: 2017-06-14 Last updated: 2018-03-13Bibliographically approved
Chen, L., Hang, J., Sandberg, M., Claesson, L. & Di Sabatino, S. (2017). The Influence of Building Packing Densities on Flow Adjustment and City Breathability in Urban-like Geometries. Procedia Engineering, 198, 758-769
Open this publication in new window or tab >>The Influence of Building Packing Densities on Flow Adjustment and City Breathability in Urban-like Geometries
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2017 (English)In: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 198, p. 758-769Article in journal (Refereed) Published
Abstract [en]

City breathability refers to the air exchange process between the flows above and within urban canopy layers (UCL) and that of in-canopy flow, measuring the potential of wind to remove and dilute pollutants, heat and other scalars in a city. Bulk flow parameters such as in-canopy velocity (Uc) and exchange velocity (UE) have been applied to evaluate the city breathability. Both wind tunnel experiments and computational fluid dynamics (CFD) simulations were used to study the flow adjustment and the variation of city breathability through urban-like models with different building packing densities. We experimentally studied some 25-row and 15-column aligned cubic building arrays (the building width B=72 mm and building heights H=B) in a closed-circuit boundary layer wind tunnel. Effect of building packing densities (λp=λf=0.11, 0.25, 0.44) on flow adjustment and drag force of each buildings were measured. Wind tunnel data show that wind speed decreases quickly through building arrays due to strong building drag. The first upstream building induces the strongest flow resistance. The flow adjustment length varies slightly with building packing densities. Larger building packing density produces lower drag force by individual buildings and attains smaller velocity in urban canopy layers, which causes weaker city breathability capacity. In CFD simulations, we performed seven test cases with various building packing densities of λp=λf=0.0625, 0.11, 0.25, 0.36, 0.44 and 0.56. In the cases of λp=λf=0.11, 0.25, 0.44, the simulated profiles of velocity and drag force agree with experiment data well. We computed Uc and UE, which represent horizontal and vertical ventilation capacity respectively. The inlet velocity at 2.5 times building height in the upstream free flow is defined as the reference velocity Uref. Results show that UE/Uref changes slightly (1.1% to 0.7%) but Uc/Uref significantly decreases from 0.4 to 0.1 as building packing densities rise from 0.0625 to 0.56. Although UE is induced by both mean flows and turbulent momentum flux across the top surface of urban canopy, vertical turbulent diffusion is found to contribute mostly to UE.

Place, publisher, year, edition, pages
Elsevier Ltd, 2017
Keywords
Building packing densiy, City breahability, Exchange velocity, Flow adjustment, In-canopy velocity, Atmospheric thermodynamics, Boundary layer flow, Boundary layers, Computational fluid dynamics, Drag, Velocity, Wind, Wind tunnels, Boundary layer wind tunnel, Computational fluid dynamics simulations, Turbulent momentum fluxes, Vertical ventilation, Wind tunnel experiment, Buildings
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-25416 (URN)10.1016/j.proeng.2017.07.127 (DOI)000425682900067 ()2-s2.0-85029853562 (Scopus ID)
Note

Funding details:

- MOE, Ministry of Education;

- Grant no: 2013U-5, THU, Tsinghua University

- Grant no: 51478486, NSFC, National Natural Science Foundation of China

Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2018-03-20Bibliographically approved
Sandberg, M., Mattsson, M., Wigö, H., Hayati, A., Claesson, L., Linden, E. & Khan, M. (2015). Viewpoints on wind and air infiltration phenomena at buildings illustrated by field and model studies. Building and Environment, 92, 504-517
Open this publication in new window or tab >>Viewpoints on wind and air infiltration phenomena at buildings illustrated by field and model studies
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2015 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 504-517Article in journal (Refereed) Published
Abstract [en]

Ventilation and infiltration caused by wind are difficult to predict because they are non-local phenomena: driving factors depend on the surrounding terrain and neighbouring buildings and on the building orientation with respect to the wind direction. Wind-driven flow through an opening is complex because wind can flow through the opening or around the building, in contrast to buoyancy driven flow. We explored wind and air infiltration phenomena in terms of pressure distributions on and around buildings, stagnation points, flow along façades, drag forces, and air flow through openings. Field trials were conducted at a 19th-century church, and wind tunnel tests were conducted using a 1:200 scale model of the church and other models with openings.

 

The locations of stagnation points on the church model were determined using particle image velocimetry measurements. Multiple stagnation points occurred. The forces exerted on the church model by winds in various directions were measured using a load cell. The projected areas affected by winds in various directions were calculated using a CAD model of the church. The area-averaged pressure difference across the church was assessed. A fairly large region of influence on the ground, caused by blockage of the wind, was revealed by testing the scale model in the wind tunnel and recording the static pressure on the ground at many points. The findings of this study are summarized as a number of steps that we suggest to be taken to improve analysis and predictions of wind driven flow in buildings.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Infiltration, Wind, Particle Image Velocimetry, Openings, Stagnation points, Drag force
National Category
Building Technologies
Identifiers
urn:nbn:se:hig:diva-19278 (URN)10.1016/j.buildenv.2015.05.001 (DOI)000358807800046 ()2-s2.0-84930645066 (Scopus ID)
Projects
Church project
Funder
Swedish Energy Agency, 34964-1
Available from: 2015-05-04 Created: 2015-05-04 Last updated: 2018-12-03Bibliographically approved
Mattsson, M., Sandberg, M., Claesson, L., Lindström, S. & Hayati, A. (2013). Fan pressurization method for measuring air leakage in churches – wind and stack induced uncertainties. In: A. Troi and E. Luchi. (Ed.), Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation: . Paper presented at Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation (EWCHP), Bozen, Italy, September 16-17, 2013 (pp. 63-68).
Open this publication in new window or tab >>Fan pressurization method for measuring air leakage in churches – wind and stack induced uncertainties
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2013 (English)In: Conference proceedings: Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation / [ed] A. Troi and E. Luchi., 2013, p. 63-68Conference paper, Published paper (Refereed)
Abstract [en]

The air leakage of the building envelope of ancient churches and other historical and monumental buildings has impact on energy consumption, thermal comfort, humidity and indoor surface soiling. To measure the air leakage in such large and naturally ventilated single-zone buildings is however challenging, especially due to wind and buoyancy (stack) induced disturbances. This study describes experiences in this regard, attainedat field tests where the fan pressurization technique (“Blower door”) was employed. Reference is made to the European test standard EN 13829. Also results of wind-tunnel tests are utilized. It is shown that both buoyancy and wind at commonly occurring conditions can cause significant uncertainty in fan pressurization tests, and that some of the directions in the standard might need to be strengthened or amended. While the uncertainty in measured air leakage rate at the standard (high) pressure of 50 Pa may be small, the predictions of the air leakage rate occurring at realistically (low) indoor-outdoor pressures tend to suffer from significant uncertainty. That uncertainty is then conveyed to later utilizations of the test results, e.g. building energy modeling and prediction. It is also shown that the wind induced pressure at buildings like churches extends a considerable way out into the surroundings of the building; in the order of two times the building height. This has particular importance when choosing a reference point for outdoorpressure measurement.

Keywords
Fan pressurization, Blower door, Large buildings, Churches, Wind effects, Stack effects
National Category
Building Technologies
Identifiers
urn:nbn:se:hig:diva-15409 (URN)978-88-88307-26-8 (ISBN)
Conference
Cultural heritage preservation – 3rd European Workshop on Cultural Heritage Preservation (EWCHP), Bozen, Italy, September 16-17, 2013
Projects
Church project
Funder
Swedish Energy Agency, 2011-002440
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2018-12-03Bibliographically approved
Sandberg, M., Wigö, H., Claesson, L. & Cehlin, M. (2011). A wind tunnel method for screening the interaction between wind turbines in planned wind farms. In: Wrec 2011 Linköping Sweden 2011: . Paper presented at The World Renewable Energy Congress 2011.
Open this publication in new window or tab >>A wind tunnel method for screening the interaction between wind turbines in planned wind farms
2011 (English)In: Wrec 2011 Linköping Sweden 2011, 2011Conference paper, Published paper (Refereed)
Keywords
Wind farms Pressure distribution on ground Wind tunnel
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hig:diva-10136 (URN)
Conference
The World Renewable Energy Congress 2011
Available from: 2011-09-15 Created: 2011-09-15 Last updated: 2018-12-03Bibliographically approved
Sandberg, M., Mattsson, M., Etheridge, D. W. & Claesson, L. (2011). Wind tunnel measurements of pressure distribution on  the facade of a church. In: Tor Broström & Lisa Nilsen (Ed.), Proc. EEHB 2011: Conference on Energy Efficiency in Historic Buildings. Paper presented at EEHB 2011: Conference on Energy Efficiency in Historic Buildings. Visby. Sweden.. Visby: Gotland University Press
Open this publication in new window or tab >>Wind tunnel measurements of pressure distribution on  the facade of a church
2011 (English)In: Proc. EEHB 2011: Conference on Energy Efficiency in Historic Buildings / [ed] Tor Broström & Lisa Nilsen, Visby: Gotland University Press, 2011Conference paper, Published paper (Refereed)
Abstract [en]

Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation. A model in scale 1: 200 was built of a 19th century Swedish church provided with a crawl space.The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church, dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space.  Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper. With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

Place, publisher, year, edition, pages
Visby: Gotland University Press, 2011
Keywords
Wind pressure coefficient, Building surface, Wind tunnel, Church, Air infiltration
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:hig:diva-9258 (URN)978-91-86343-11-8 (ISBN)
Conference
EEHB 2011: Conference on Energy Efficiency in Historic Buildings. Visby. Sweden.
Projects
Church project
Available from: 2011-05-13 Created: 2011-05-13 Last updated: 2018-12-03Bibliographically approved
Sandberg, M., Mattsson, M., Etheridge, D. W. & Claesson, L. (2011). Wind tunnel measurements of pressure distribution on the façade and surrounding ground of a church. In: Hans Martin Mathisen (Ed.), Roomvent 2011: 12th International conference on air distribution in rooms. Paper presented at Roomvent 2011: 12th International conference on air distribution in rooms. Paper No. 274. Trondheim. Norway.. Trondheim, Norge: Tapir Akademisk Forlag
Open this publication in new window or tab >>Wind tunnel measurements of pressure distribution on the façade and surrounding ground of a church
2011 (English)In: Roomvent 2011: 12th International conference on air distribution in rooms / [ed] Hans Martin Mathisen, Trondheim, Norge: Tapir Akademisk Forlag , 2011Conference paper, Published paper (Refereed)
Abstract [en]

Elderly churches have a unique shape with their high towers and long naves. There seems to be few if any reported measurement of pressure distribution on churches. Churches are naturally ventilated buildings and therefore when the wind speed is high  the  wind becomes an important driving force for ventilation.

A model in scale 1:200 was built of a 19th century Swedish church provided with a crawl space. The pressure on the façade of the model was recorded in 42 points. With the aim of studying the ventilation of the church dedicated measuring points were located on windows, doors and in the positions corresponding to the location of the openings in the crawl space. 

Some field trials were undertaken with the scope of measuring the time history of the static pressure on the façade in some positions corresponding to measuring points on the wind tunnel model. Examples of these measurements are  reported in the paper.

With the aim of measuring the “region of influence” on the ground caused by the church, also the static pressure on the ground was recorded in the wind tunnel tests.  The static pressure on ground was recorded with a pressure plate provided with 400 pressure taps arranged in a quadratic pattern.

Place, publisher, year, edition, pages
Trondheim, Norge: Tapir Akademisk Forlag, 2011
Keywords
Wind tunnel, Church, Wind pressure coefficient, Crawl space, Ground
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:hig:diva-9259 (URN)9788251928120 (ISBN)
Conference
Roomvent 2011: 12th International conference on air distribution in rooms. Paper No. 274. Trondheim. Norway.
Projects
Church project
Available from: 2011-05-13 Created: 2011-05-13 Last updated: 2018-12-03Bibliographically approved
Kobayashi, T., Sandberg, M., Kotani, H. & Claesson, L. (2010). Experimental investigation and CFD analysis of cross-ventilated flow through single room detached house model. Building and Environment, 45(12), 2723-2734
Open this publication in new window or tab >>Experimental investigation and CFD analysis of cross-ventilated flow through single room detached house model
2010 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 12, p. 2723-2734Article in journal (Refereed) Published
Abstract [en]

Cross-ventilation is a complicated flow problem and difficult to control because wind exhibits a large degree of variation. The paper focuses on three items: a) to clarify and understand some of the basic characteristics of airflow as the influence of the opening size on the windward vortex and the leeward wake; b) to explore what information about the flow above the ground can be retrieved from pressure measurements on the ground; and c) to explore the accuracy of CFD. To meet these objectives, wind tunnel tests and CFD analyses were carried out. The studied object was a detached-house model provided with two openings. The size of these openings was changed in a wide range from narrow cracks to large openings. In the experiments, pressure measurements on the ground and PIV measurements were made. The internal flow was visualized with the sand erosion method. Pressure measurement on a floor surface is a relatively easy and an inexpensive method. In this experiment, the windward and leeward areas in particular were investigated to understand flow pattern and to confirm correspondence between flow pattern and recorded pressure on the ground. Those measurements show the difference in flow at different size openings in terms of the vortex on the windward side and the wake. When the size of the opening exceeded a certain value the near wake on the leeward side disappeared and on the windward side the vortex disappeared. The pressure distribution, flow pattern, and velocity profile are shown and compared between measurement and CFD.

Keywords
Cross-ventilation, Wind tunnel, PlV, Pressure measurement, CFD, Reynolds stress model
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-10264 (URN)10.1016/j.buildenv.2010.06.001 (DOI)000281326800013 ()2-s2.0-77955425539 (Scopus ID)
Available from: 2011-09-21 Created: 2011-09-21 Last updated: 2018-12-03Bibliographically approved
Hang, J., Sandberg, M., Li, Y. & Claesson, L. (2010). Flow mechanisms and flow capacity in idealized long-street models. Building and Environment, 45(4), 1042-1053
Open this publication in new window or tab >>Flow mechanisms and flow capacity in idealized long-street models
2010 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 45, no 4, p. 1042-1053Article in journal (Refereed) Published
Abstract [en]

It is an open question whether a street network of a city has a certain flow capacity characterizing the flow that can pass through the street network. It s our hypothesis that at least the simple street network has a certain flow capacity. With the purpose of exploring this we studied numerically and experimentally the flow capacity in some idealized long-street models continuously lined with buildings and exposed to a parallel approaching wind. The height of all the models is the same (H = 69 mm). Three groups of models were studied: models with the same uniform street width (W = H) but different lengths (L = 21.7H, 43.5H, 72.5H); models with the same length (L = 43.5H) but different uniform width (W = H, 2H, 4H); and models with a change of width at half distance, L/2. In the last of the three cases, the width of the upstream half was always the same (W1 = H), but there was a wider (W2 = 1.25H, 1.5H, 2H) or narrower (W2 = 0.75H, 0.5H) downstream half. We normalized flow rates by a reference flow rate equal to the flow rate through an opening far upstream with the same area as the windward entry. The normalized flow rate through the windward entry was about 1.0 in all cases. For a sufficiently long-street models, a flow balance is established, creating a fully developed region with a constant horizontal flow (flow capacity) and zero vertical mean velocity. The street length does not affect the flow capacity but as expected the width of the street affects the flow capacity.

Keywords
CFD, Wind tunnel, Long Streets; Aspect ratio, Flow rate, Total Energy density
National Category
Civil Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:hig:diva-6485 (URN)10.1016/j.buildenv.2009.10.014 (DOI)000273945300030 ()2-s2.0-71649098131 (Scopus ID)
Available from: 2010-03-05 Created: 2010-03-04 Last updated: 2018-12-03Bibliographically approved
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