scholarly journals Combined Use of Wind-Driven Rain Load and Potential Evaporation to Evaluate Moisture Damage Risk: Case Study on the Parliament Buildings in Ottawa, Canada

Buildings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 476
Author(s):  
Aytaç Kubilay ◽  
John Bourcet ◽  
Jessica Gravel ◽  
Xiaohai Zhou ◽  
Travis V. Moore ◽  
...  
Keyword(s):  
Freezing Point ◽  
Meteorological Data ◽  
Building Envelope ◽  
Moisture Determination ◽  
Fast Method ◽  
Potential Evaporation ◽  
Critical Periods ◽  
Freeze Thaw ◽  
Combined Use ◽  
Computational Fluid Dynamics Cfd

Parts of the building envelope that frequently receive high amounts of rain are usually exposed to a higher risk of deterioration due to moisture. Determination of such locations can thus help with the assessment of moisture-induced damage risks. This study performs computational fluid dynamics (CFD) simulations of wind-driven rain (WDR) on the Parliament buildings in Ottawa, Canada. Long-term time-varying wetting load due to WDR and potential evaporation are considered according to several years of meteorological data, and this cumulative assessment is proposed as a fast method to identify critical locations and periods. The results show that, on the Center Block of the Parliament buildings, the façades of lower towers facing east are the most exposed to WDR, together with the corners of the main tower. Periods of high WDR wetting load larger than the potential evaporation are observed, indicating that deposited rain may lead to moisture accumulation in the envelope. During these critical periods of up to several months, air temperature may repeatedly drop below freezing point, which poses a risk of freeze–thaw damage. First assessment on future freeze–thaw damage risks indicates an increase in such risks at moderate increases in temperature, but a lower risk is found for larger increases in temperature.

scholarly journals Freezing point depression and freeze-thaw damage by nanofluidic salt trapping

2020 ◽  
Vol 5 (12) ◽  
Author(s):  
Tingtao Zhou ◽  
Mohammad Mirzadeh ◽  
Roland J.-M. Pellenq ◽  
Martin Z. Bazant
Keyword(s):  
Freezing Point ◽  
Freezing Point Depression ◽  
Freeze Thaw

scholarly journals Impact of climate change and human activity on the runoff in the upper reaches of the Shiyang River, Northwest China

2014 ◽  
Author(s):  
Peng Li ◽  
Jianhua Xu ◽  
Zhongsheng Chen ◽  
Benfu Zhao
Keyword(s):  
Climate Change ◽  
Human Activity ◽  
Climatic Factors ◽  
Meteorological Data ◽  
Northwest China ◽  
Potential Evaporation ◽  
The Past ◽  
Shiyang River Basin ◽  
Runoff Change ◽  
Increasing Trend

Based on the hydrological and meteorological data of the upper reaches of Shiyang River basin in Northwest China from 1960 to 2009, this paper analyzed the change in runoff and its related climatic factors, and estimated the contribution of climate change and human activity to runoff change by using the moving T test, cumulative analysis of anomalies and multiple regression analysis. The results showed that temperature revealed a significant increasing trend, and potential evaporation capacity decreased significantly, while precipitation increased insignificantly in the past recent 50 years. Although there were three mutations in 1975, 1990 and 2002 respectively, runoff presented a slight decreasing trend in the whole period. The contributions of climate change and human activity to runoff change during the period of 1976-2009 were 45% and 55% respectively.

The role of freezing-thaw cycling in rock samples topography evolution and rock cliff retreat

2021 ◽  
Author(s):  
Li Fei ◽  
Marc-Henri Derron ◽  
Tiggi Choanji ◽  
Michel Jaboyedoff ◽  
Chunwei Sun ◽  
...  
Keyword(s):  
Freezing Point ◽  
Meteorological Data ◽  
Test Chamber ◽  
Monitoring Program ◽  
Dynamic Environment ◽  
Rock Properties ◽  
Rock Surface ◽  
Physical Weathering ◽  
Rock Samples

<p>Freezing-thaw weathering is recognized as one of the most significant factors in the fatigue of rock mass in areas where the temperature periodically fluctuates around the freezing point. <br>A one-year monthly SfM monitoring program from December 19, 2019, to January 7, 2021, was done to detect rockfall activity on a rockslide cliff composed of marl-sandstone at La Cornalle, Switzerland. More than one hundred rockfall events were detected during this period with the volumes varied from 0.005m<sup>3</sup> to 4.85m<sup>3</sup>. <br>We texture all the rockfalls on the 3D SfM model. It is shown that most of them are mainly located in three areas:  the top of the cliff, the foot of the cliff, and the medium-left part of the cliff. The common feature of these three parts is that the layers are more or less overhanging with dense fractures around them. At the same time, the meteorological data collected by a weather station on site is correlated with the rockfall events to figure out the relationship between each other. Actually, about 30% of total rockfall volume fell during winter on this site. The triggering factor of rockfall during winter is related to freezing-thaw cycling. This kind of weathering can be understood as an interplay between rock properties and its dynamic environment.<br>In order to make clear the role of freezing-thaw played on the rockfall generation, an on-site 24h monitoring measurement program that consists of two crack meters, one rock thermal sensor, and thermal camera monitoring is installed in January 2021. Those datasets will help to understand how the crack grows with the changing temperature. In addition, freezing-thaw cycling laboratory experiments for the rock samples taken from different areas of the cliff will be done with an environmental test chamber. The topography of the rock samples before and after the experiments will be acquired by a 3D handheld scanner. This work will benefit to reveal the rock surface evolution during the freezing-thaw cycling in a dynamic environment with varied humidity and number of cycles. <br>In conclusion, the combination of on-site measurements and laboratory freezing-thaw experiments will provide a good basis for a better understanding of the rockfall triggering mechanism led by physical weathering.</p>

Automated Optimum Design of Refrigerated Warehouses

1979 ◽  
Vol 101 (4) ◽  
pp. 633-639
Author(s):  
B. D. Gupta ◽  
S. S. Rao
Keyword(s):  
Optimum Design ◽  
Meteorological Data ◽  
Operating Cost ◽  
Building Envelope ◽  
Penalty Function Method ◽  
Functional Requirements ◽  
Existing Building ◽  
Total Cost ◽  
Initial Cost ◽  
Average Maximum

The main consideration in the design of refrigerated commercial warehouses, apart from energy required for operation, is the total cost (initial plus operating costs). There is no simple explicit relation between the total cost and the energy required to maintain the desired inside conditions. Qualitatively, one feels that a design involving less initial cost requires larger energy input and hence a higher operating cost. With limited energy resources, it is necessary to conserve energy or use it optimally. A unified approach to find the optimal combination of initial cost and operating cost (energy) is presented in this paper. Since the thickness of insulation is one of the important factors to be considered in reducing the external load and hence the energy requirements, the optimum building envelope and insulation thicknesses are found for a specified volume and location by using the interior penalty function method of optimization. The procedure outlined in this paper can be used for new as well as existing building to fulfill the functional requirements optimally and thus conserve the energy to the greatest possible extent. For the computation of heat gain, the design day, based on the average maximum solar air temperature computed from the hourly meteorological data, is chosen. The resulting computer program is used to find the effect of some of the parameters like wall thickness, type of insulation, orientation of building and economics model on the optimum design.

Numerical analysis of local thermal comfort in a plan office under natural ventilation

2019 ◽  
Vol 29 (7) ◽  
pp. 972-986 ◽  
Author(s):  
Xiang Deng ◽  
Zijing Tan
Keyword(s):  
Thermal Comfort ◽  
Natural Ventilation ◽  
Meteorological Data ◽  
Ventilation System ◽  
Comfort Level ◽  
Open Plan ◽  
Computational Fluid Dynamics Cfd ◽  
Internal Volume ◽  
Local Thermal Comfort ◽  
Primary Focus

The utilisation of automatic controlled natural wind in office buildings to maintain indoor thermal comfort has gained wide attention in recent years. Generally, it is not necessary to ensure that the whole internal volume of a building with large open spaces meets thermal comfort requirements. Primary focus should be on occupied areas. Accordingly, the local thermal comfort in an open-plan office with automatic controlled natural ventilation system was investigated numerically and experimentally. A computational fluid dynamics (CFD)-based method was presented for indoor environment and thermal comfort prediction. Long-term in situ measurement was conducted during summer and transition seasons. The meteorological data were collected by a mini weather station located on the roof of the target building. Meanwhile, indoor air velocity, temperature, turbulence intensity and wall temperatures were recorded locally. Three thermal comfort indices, i.e. thermal stratification represented by percentage dissatisfied (PD), the extended predicted mean vote (PMVe) and draught rate were employed to evaluate the thermal comfort level of the interested areas during natural ventilation period. The numerical results revealed a risk of local thermal dissatisfaction under low outdoor temperature and strong windy conditions.

Deciphering Rainfall and Freeze thaw cycles as long-term preparatory factors for alpine rockfalls

2020 ◽  
Author(s):  
Greta Bajni ◽  
Corrado Camera ◽  
Tiziana Apuani
Keyword(s):  
Landslide Susceptibility ◽  
Meteorological Data ◽  
Meteorological Conditions ◽  
Climatic Variables ◽  
Time Interval ◽  
Reference Period ◽  
Time Intervals ◽  
Long Term Conditions ◽  
Freeze Thaw

<p>Due to climate change and the strong relationships between landslides and atmospheric variables, the concept of a stationary landslide susceptibility appears limited. However, relating landslides with climatic predisposing and triggering factors is challenging, due to the lack of multitemporal event datasets. Rockfalls are even more challenging in this context, as their reaction to meteorological events is connected to widely variable characteristics (e.g. rock type, in situ stress, fracture network).</p><p>By exploiting and homogenizing a multitemporal rockfall inventory and meteorological datasets of the Aosta Valley Region (Western Italian Alps), the general goal of our study was to develop a procedure to decipher the effects of both the short- and long-term action of rainfall and freeze-thaw cycles on rockfalls occurrence, recognized as main forcing climatic variables in the classic literature. Our specific objective was to define synthetic and effective meteorological variables that can act as predictors in statistical landslide susceptibility models.</p><p>We analysed 168 rockfall events and meteorological data from 17 stations from 1990 to 2018 (reference period) distributed on an area 670 km<sup>2</sup>. The analysis was performed considering:</p><ul><li>Short term (hourly) precipitation expressed both by the intensity-duration characteristics of the single rockfall associated rainfall(1) and by the maximum cumulated rainfall in time intervals from 0.5 to 24 hours before the event(2);</li> <li>Long term precipitation (multiple episodes) expressed both by cumulated rainfall in time interval of 1 day to 60 days (3) and by the number of rainfall episodes occurred in 1- to 12-month time intervals before the event(4);</li> <li>Number of Freeze-thaw cycles in the year before the event, identified as temperature variation crossing the 0°C value(5).  </li> </ul><p>By comparing the statistical distribution, for the whole reference period, of the above mentioned climatic variables and the meteorological conditions before each rockfall event, we recognized four types of not ordinary climatic conditions. All conditions resulted to be associated to long term conditions of any time interval, while hourly intervals did not result significant. Type-a is associated to cumulated rainfall overcoming the 90<sup>th</sup> percentile of the historical time series(69 out of 168); Type-b to a number of rainfall episodes higher than the 75<sup>th</sup> percentile value(70 rockfalls out of 168); Type–c to a number to a number of freeze-thaw cycles higher than the 75<sup>th</sup> percentile value(66 out of 168); Type-d to a combination of these factors (47 out of 168). Only 5 rockfalls occurred during ordinary meteorological conditions, whereas the remaining 37 rockfalls could not being analysed due to the absence of complete meteorological data.</p><p>Based on these results, we defined a long term Intensity-duration and two episode-duration thresholds, each expressed by a power law equation. The number of times, in the reference period, of exceedance of the selected thresholds represent the synthetic variables to be spatialized by means of geostatistical techniques and tested within a statistical landslide susceptibility model.</p>

Forced Response Sensitivity of a Mistuned Rotor From an Embedded Compressor Stage

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Fanny M. Besem ◽  
Robert E. Kielb ◽  
Nicole L. Key
Keyword(s):  
Axial Compressor ◽  
Forced Response ◽  
Fast Method ◽  
Forcing Function ◽  
Timing Data ◽  
Wear And Tear ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses ◽  
The Individual ◽  
Wave Coordinates

The frequency mistuning that occurs due to manufacturing variations and wear and tear of the blades has been shown to significantly affect the flutter and forced response behavior of a blade row. While tuned computational fluid dynamics (CFD) analyses are now an integral part of the design process, designers need a fast method to evaluate the localized high blade responses due to mistuning. In this research, steady and unsteady analyses are conducted on the second-stage rotor of an axial compressor, excited at the first torsion vibratory mode. A deterministic mistuning analysis is conducted using the numerical modal forces and the individual blade frequencies obtained experimentally by tip timing data. The mistuned blade responses are compared in the physical and traveling wave coordinates to the experimental data. The individual and combined impacts of frequency, aerodynamic, and forcing function perturbations on the predictions are assessed, highlighting the need to study mistuned systems probabilistically.

Effect of Zeolite Admixture on Freeze/Thaw Resistance of Concrete Exposed to the Dynamic Climatic Conditions

2014 ◽  
Vol 982 ◽  
pp. 27-31 ◽  
Author(s):  
Václav Kočí ◽  
Miloš Jerman ◽  
Jiří Maděra ◽  
Robert Černý
Keyword(s):  
Service Life ◽  
Computational Simulation ◽  
Climatic Conditions ◽  
Building Envelope ◽  
Point Of View ◽  
Freeze Thaw ◽  
Hygrothermal Behavior ◽  
Hygrothermal Performance ◽  
Concrete Building ◽  
Positive Effect

This paper aims at computational simulation of effect of zeolite admixture on service life of concrete building envelope from point of view of freeze/thaw resistance. Hygrothermal behavior of two types of concrete is studied in this paper: reference concrete without any admixtures and zeolite concrete with 40 % zeolite as cement replacement. The computations are performed using computer simulation tool HEMOT, which processes the input parameters using finite element method. The simulation is assumed under dynamic climatic conditions of Prague. As the results of the computational simulations showed, assuming analyzed amount of zeolite, any positive effect of on freeze/thaw resistance was not found related to unprotected building envelope. However, the results indicated, hygrothermal performance of zeolite concrete can be very considerate to applied external layers and thus extend their service life.

scholarly journals Freeze-Thaw Characteristics of Water-Based Copper Oxide Nanofluid

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Heat Transfer ◽  
Copper Oxide ◽  
Freezing Point ◽  
Average Particle Size ◽  
Solidification Process ◽  
Heat Transfer Fluid ◽  
Average Particle ◽  
Volumetric Concentration ◽  
Freeze Thaw ◽  
Water Based

This research examined the freeze-thaw characteristics of a water-based copper oxide (CuO) nanofluid for its successful application in cold regions, where freezing of heat transfer fluids can occur. The enhanced thermal conductivity (k) of nanofluid makes it valuable as a heat transfer fluid, but k diminishes as the average particle size (APS) of the dispersed nanoparticles grows. Therefore, experiments were conducted to determine the effect of freezing on the APS of nanofluid suspensions due to agglomeration. Additionally, it was studied, if the freezing point of the nanofluid was elevated or depressed as the volumetric concentration of nanoparticles in the suspension was increased from 1 % to 5%. Another objective of this experimental study was to compare the time required for precooling, freezing and subcooling of different concentrations of nanofluids and the base fluid. The results showed that the APS grew by as much as 51.2% larger due to the phenomenon of freezing, which would reduce the heat transfer performance. The addition of nanoparticles did not affect the freezing point of the nanofluids, tested for two particle volumetric concentrations of 1 and 5 %. It was observed that the precooling time of 5% CuO concentration was the longest. For the complete solidification process, the water and 1% CuO had comparable freezing times, while the 5% nanofluid had the shortest freezing time. The subcooling time was increased with particle volumetric concentration.

Sign in / Sign up

Export Citation Format

Share Document