Maximum Air Speed Research Articles

Trajectory planning of stratospheric airship for station-keeping mission based on improved rapidly exploring random tree

The station-keeping mission is one of the common missions of stratospheric airships. Its movement is sensitive to wind due to the large size and low airspeed of stratospheric airships. When the wind speed exceeds the maximum airspeed of the airship, the airship may fly out of the given mission region. Therefore, station-keeping trajectory planning is a new trajectory planning problem that has never existed before. A rapidly exploring random tree algorithm for station-keeping(RRT-SK) is proposed to solve the trajectory planning problem under multiple constraints of the airship, and an artificial potential field method (APF) considering wind field and relative position is designed as the objective function of the RRT-SK algorithm, both of which form the RRT-SK strategy used for the stratospheric airship station-keeping trajectory planning under multiple constraints. A multidisciplinary model is developed to simulate multiple constraints on the airship flight, including the energy model, thermal model, propulsion model, and kinematic model. The performance of the RRT-SK strategy is demonstrated in this multidisciplinary model with real wind fields. The results show that the multi-constrained station-keeping problem can be solved by the RRT-SK strategy. Compared with the conventional strategy, the RRT-SK strategy can improve the success rate of the airship’s 24-h stationing flight and well cope with the impact of wind field changes and stationing area changes. Moreover, the RRT-SK strategy has better advantages in actual long-duration use.

Research on decoupled air speed and air volume adjustment methods for air-assisted spraying in orchards.

Different fruit tree canopies have different requirements for air speed and air volume. Due to the strong relationship between air speed and air volume, the decoupled control of air speed and air volume cannot be achieved using the existing sprayers. In this study, an innovative air-assisted sprayer that supports the independent adjustment of fan speed (0-2940 r/min) and air outlet area (1022.05-2248.51 cm2) is developed, and the maximum air speed and air volume of the sprayer outlet are 45.98 m/s and 37239.94 m3/h, respectively. An independent adjustment test of the fan speed and air outlet area was carried out. The results indicated that the fan speed and air outlet area have opposing adjustment effects on air speed and air volume; decoupled control of the outlet air speed and air volume can thus be achieved through combined control of the fan speed and air outlet area. A test was carried out on combined fan speed and air outlet area control. Two decoupled air speed and air volume adjustment models were established, one with a constant air speed and variable air volume and the other with a constant air volume and variable air speed. The test results show that the air volume adjustment model with constant air speed had a maximum mean error of 1.13%, and the air speed adjustment model with constant air volume had a maximum mean error of 1.67%. The results will provide theoretical and methodological support for the development of airflow adjustment systems for orchard air-assisted sprayer.

A simulation model for the electrical rotary-wing aircraft (eVTOL) performance estimation for the urban air mobility purposes

The present paper presents a simulation model description developed for the aircraft performance estimation of the most popular electric vertical takeoff and landing aircraft (eVTOL) aerodynamic configurations with the electric (hybrid) power plant for the urban air mobility purposes. It focuses on the quadcopter-type eVTOL aircraft aerodynamic configurations using the unshrouded-propellers or ducted fans driven by electric motors. The aircraft performance analysis for aerodynamic configurations of the quadcopter and tilt rotor-quadcopters with the tilt rotors and wing with the all-electric (EP) or hybrid power plant (HP) is given. To compare aircraft performance, the estimation results for a conventional single-rotor helicopter with EP or HP are given. Based on the numerical solution equation of the aircraft existence, feasible structural components mass distributions for various types of eVTOL configurations were obtained. eVTOL aircraft performance, including the estimation of apparent and drag power for the airspeed range, from hovering to the maximum airspeed, as well as for the transition modes (tilt rotor aircraft and quadcopters) were estimated. The eVTOL aircraft flight range and duration with EP and HP at the straight and level flight mode were calculated. Specific mass characteristics of EP and HP components (batteries, generators, electric motors, etc.) to ensure acceptable eVTOL aircraft performance were identified. A comparative evaluation of considered eVTOL configurations for the purpose of their efficiency was performed. Aerodynamic calculations were carried out based on the known analytical techniques of the lifting propeller momentum theory with the data correction capability according to test results. The simulation model, obtained in this paper, can be considered in the phase of the preliminary choice as the first approach of structural parameters and aerodynamic configurations of prospective electric (hybrid) eVTOLs designed for the use as an urban air taxi.

Flow field analysis of combustion fallout propensity test system based on CFD

AbstractThe flow field of the environment plays a crucial role in cigarette combustion cone fallout propensity test, with air velocity exhibiting a positive correlation with combustion volume. In order to minimize the impact of the environmental flow field on the test results, it is necessary to control the air speed within the range of 200 ± 30 mm/s in the test area of each tobacco test channel. To address this concern, which used the Realizable k‐ε model to develop a mathematical model of the testing environment. The uniformity of air speed in each channel and its relationship with structural parameters were then analyzed. Based on these findings, the key structural parameters of the ventilation hood are optimized. After restimulated the optimized model, the results demonstrate a higher level of uniformity in the environmental flow field of the optimized section. To validate the accuracy of the simulation results, measurements indicated that the maximum air speed value at all points is 225.6 mm/s, while the minimum value is 178.44 mm/s. These values fall within the specified range of 200 ± 30 mm/s, thus meeting the design requirements. This study ensures that the cigarette can burn in a steady state during the cigarette combustion fallout propensity test and improves the stability of the cigarette combustion cone drop tendency test results.

The Development of Aerobic Capacity between the Short-term Training 15"/15" and the Long-term Training 3'/3' for Soccer Players U21

The study aims to identify the type of interval exercises that have an effective impact on developing some aerobic capacities (maximum airspeed - VMA, maximum oxygen consumption - VO2MAX) for football players U21. The researchers proposed two training programs for a sample of 16 players from the youth team of JSMTairet activity in the amateur second division of the Algerian championship center-west for the season 2021/2022. The sample was divided into two groups, where the first group applied the proposed training program using long-term interval training method of 3'/3', while the second group applied the program using short-term interval training method of 15” /15”. The proposed training program lasted for 8 weeks, with two sessions per week, under the supervision of the research team. The Intermittent Fitness Test 30/15 IFT was used to measure the rate of aerobic capacities VMA/VO2MAX. After obtaining, processing, analyzing, and interpreting the results, it was found that there were statistically significant differences between the post-tests of the two groups. This suggests that training with short-term interval exercises improves the level of aerobic capacities VMA/VO2MAX for football players. Therefore, the researchers recommend using short-term interval exercises during planning and preparation of training programs in different preparation and competition periods to develop physical fitness for players and achieve the highest levels of sports achievement.

Design and Manufacturing of Wind Tunnel for Turbine Impeller Airfoil Testing

In this study, the design of a wind tunnel was carried out to observe airflow through an airfoil, streamlines and turbine blades. To accommodate this, in this study a design was made of an open return wind tunnel. In this case, an open circuit wind tunnel type will be made because the construction is simpler and the manufacturing costs are relatively cheaper compared to the closed circuit wind tunnel type. The Wind Tunnel is designed with Open CLosed Wind Tunnel (OCWT) type. The OCWT is designed to consist of fan and housing, diffuser, test section, contraction, honeycomb. The OCWT design uses an operating fan to circulate air into the test section. The maximum air speed in the Test Section is 5 m/s with a flow that is closed to laminar. The recommended diffuser has a dimension of 50 cm on the side that is attached to the test section and 52 cm on the side facing the fan with an inclination angle of 1.79o. The driver uses a 16 inch exhaust fan with a power of 74 W to make the flow in the Test Section stable at a speed of 2 m/s.

Influence of permeability ratio on wind-driven ventilation and cooling load of mid-rise buildings

Natural ventilation potential in terraced buildings is affected by numerous parameters such as permeability ratio, distribution pattern, depth of terraces, etc. This research aims to evaluate the impact of permeability ratio on natural ventilation potential and cooling load of a terraced office building in the hot- humid climate. To this end, one solid block and eight porous models with different permeability ratios (20 %–30 %–40 %–50 %) and random distribution patterns were simulated and analyzed by Energyplus engine and computational fluid dynamics (CFD). For better comparison, two distribution patterns for each permeability ratio were simulated. CFD simulations were validated according to the wind-tunnel measurements. The cooling load amount, mean and maximum airspeed as well as the mean age of air in terraces and offices were used to evaluate the best configurations of porous buildings.The results show that increasing the permeability up to 50 % will enhance the interior and inlet airspeed by 38.59 % and 49.07 % compared to the solid case. Simulations proved that a small change in porosities from 20 % to 30 % resulted in a significant difference in mean and maximum airspeed in terraces. The case with 50 % permeability ratio indicated higher values of mean and maximum airspeed in terraces. The mean age of air amount follows a descending process from the permeability ratio of 0–30 % and then increases gradually. The 30 % porous model with 30.8 s mean age of air is considered as the best case.According to the results, the introduction of permeability does not leave a positive effect on cooling energy demand despite natural ventilation performance. Although porosity reduces the solar radiation heat gain and increases the natural ventilation potential, porous models indicated high values of cooling energy consumption. This is due to the high amount of exposed surface area in porous models which leads to an increase of cooling energy demand up to 2.7 % compared to the solid case.As a result, among the permeable models, the best natural ventilation performance and the lowest cooling energy consumption are attributed to 50 % and 20 % permeable groups respectively.This study helps the designers to better understand the ventilation and energy performance of a porous model and to improve the energy-efficient buildings in hot-humid regions.

Wind energy applied as a sustainable technology to produce electrical energy in Basra

Wind energy is one of the main renewable energy sources that applied as sustainable technology to produce electricity. It is an environmentally friendly system that generating electricity without using any consumable materials and without producing any greenhouse gases and waste. In this research, a horizontal upwind turbine system was designed and manufactured with three blades using polyvinyl chloride PVC and high-density polyethylene HDPE, Aluminium and carbon steel material. It was applied to study the efficiency of the wind energy system in Basra to produce electricity in different airspeed and directions. The results show that the maximum airspeed in Basra is 6 m/s at a height of 4 m which produced 21 Volt and 1323 Watt. The greatest range of speed is 4-5 m/s on the south, east and north. However, the lowest airspeed is 2.45-3.5 m/s on west direction. Moreover, PVC material is not suitable to produce wind blades because it is broken fast due to a sudden change in the air direction.

Recovery trajectory optimization of the solar-powered stratospheric airship for the station-keeping mission

Recently, the station-keeping of the stratospheric airship is an attractive topic due to its application to provide long-endurance communication and surveillance services. The motion of the stratospheric airship is sensitive to the wind because of the characteristics of large volume and low airspeed. When the wind speed exceeds the maximum airspeed, the airship may float out of the given station-keeping region. In such a case, how to recover to the station-keeping site is a necessary problem to consider. In this paper, the recovery trajectory optimization of the stratospheric airship is discussed and the purpose is to find the economical recovery flight trajectory to the station-keeping site. The trajectory optimization model is established by considering the motion model of the stratospheric airship, the atmospheric model, the wind field model, the solar radiation model, and the thermal model. To represent the exploitation of solar energy during the flight, the solar radiation collection problem is modeled for the airship whose hull is approximated by the double-ellipsoid geometry. Then the recovery trajectory optimization problem is formulated with constraints consideration and three recovery flight scenarios are put forward. The trajectory optimization problem is transformed into the nonlinear programming problem (NLP) by the orthogonal collocation and can be solved by the off-the-shelf NLP solver. The accuracy of the solution is improved by a modified ph-adaptive mesh refinement method. Two study cases are carried out to make a profound study of the recovery flight problem. In the first case, the basic characteristics of the flight trajectories using different recovery flight scenarios are compared and analyzed. Then the influence of the solar position on the recovery trajectory is discussed in the second case, which also gives some insights on the flight characteristics of the solar-powered stratospheric airship. The results of this paper may provide some important references for the station-keeping application of the stratospheric airship.

Analytical study of an isolated coaxial rotor system with lift offset

An analytical study, which is based on calculations from a rotorcraft comprehensive analysis of a notional coaxial rotor system in isolation, is presented to improve understanding of the aeromechanics of lift-offset coaxial rotors. The calculations include a trim analysis that enforces a fixed value for coaxial system lift in order to isolate the effect of lift offset. The quantities examined here are the blade pitch controls, coaxial system performance, blade airloads, blade structural loads, and coaxial system hub loads. Operating conditions examined form airspeed sweeps for four different values of lift offset. The maximum airspeed that the rotor may achieve trim is increased by increasing lift offset. For a given airspeed, increasing lift offset generally increases the coaxial system lift-to-effective-drag ratio as a result of a decrease in shaft power (despite an increase in drag power). Increasing lift offset decreases half peak-to-peak values of pitch link force, torsion moment, and in many cases, chord bending moment. While increasing lift offset increases half peak-to-peak flap bending moment for sufficiently low airspeeds, it may decrease this quantity for higher airspeeds. Lastly, increasing lift offset generally decreases the fixed-frame, vibratory, system hub longitudinal force and pitch moment.

A Study on Developing Ventilation in Restaurants in Re-purposed Row Houses

The building ventilation of seventy-seven row houses in eight districts in Chiang Mai province of Thailand was surveyed and investigated. A typical row house re-purposed as a restaurant refers to a 3.5 m high space with two stoves in the front of the building and a closed rear area to serve as storage. As a base-case, restaurants had an average capacity of 24 customers in the dining area. Measurements of internal air quality of a selected restaurant were conducted in the summer season of 2015 and 2017, and the results revealed average air temperatures of 36°C and 33°C, relative humidity values of 46% and 33%, and air speed values of 0.28 m s-1 and 0.10 m s-1, respectively. The Computerised Fluid Dynamics (CFD) and the Center for the Built Environment (CBE) thermal comfort tool were used to simulate the efficiency of current and proposed ventilation techniques and also analyse thermal comfort conditions for each scenario. Low-cost cooling techniques of air speed and humidity adjustment were chosen to improve thermal conductions. By applying the combined techniques, the overall temperature was reduced by 2°C and the thermal comfort levels were improved from the ‘hot’ to the ‘warm’ zone. Some conditions in the second restaurant are in the expanded ‘adaptive thermal comfort zone’. Although most results appear to exceed the ‘adaptive thermal comfort zone’, conditions could not be further ameliorated since 1.5 m s-1 was the maximum air speed that could be employed in the dining area to avoid wind discomfort. Limited investment in ventilation improvement was the main challenge since air-conditioners and multiple fans were not affordable and were also insufficient for the re-adaptation option. Feasibility study of ventilation improvement technique is limited in this study.

Numerical Investigation of Deep Dynamic Stall for a Helicopter Blade Section

For helicopters in forward flight at high advance ratios, because of the cyclic variation of the angle of attack, the flow over the retreating blade can stall. This phenomenon, which is known as dynamic stall, limits the maximum airspeed of the helicopter. Physical understanding of the highly complex unsteady flow can serve as a catalyst for the development of novel flow control strategies that counter the detrimental effects of dynamic stall. For the present implicit large-eddy simulations, the complex flow over a rotor blade section with a Sikorsky SCC-A09 airfoil is decomposed into a pitching, surging, and yawing flow (dynamic crossflow). The heaving/plunging motion resulting from the unsteady blade bending under load is disregarded. Instead, the centrifugal and Coriolis accelerations are modeled. Three different combinations of the elementary flows are considered: 1) pitching and surging (baseline); 2) pitching, surging, and rotational accelerations; and 3) pitching, surging, and yawing. Simulations for an outboard blade section at a chord-based Reynolds number and a reduced frequency exhibit all relevant stages of dynamic stall reported in the literature: The bursting of a laminar leading-edge bubble is followed by the emergence of a strong dynamic stall vortex, which is eventually shed. When the harmonic yawing motion is added, the laminar bubble bursts earlier and the dynamic stall vortex is shed sooner. The addition of the rotational accelerations reduces the coherence of the dynamic stall vortex and, as a result, diminishes the cycle-to-cycle variations of the lift coefficient.

Hybrid Experimental Rocket Stuttgart: A Low-Cost Technology Demonstrator

On 8 November 2016 at 1030 hrs, the Hybrid Experimental Rocket Stuttgart (HEROS) 3 was launched from the European Space and Sounding Rocket Range (ESRANGE) Space Center to an apogee altitude of 32,300 m (106,000 ft). This set a new altitude record for European student and amateur rocketry and a world altitude record for hybrid rockets built by students. The 7.5-m-long rocket was using nitrous oxide () and a paraffin-based fuel to produce 10,000 N of thrust. The dry mass of the rocket was only 75 kg thanks to a carbon fiber structure for the most part. The rocket performed the record-breaking flight at perfect weather and visibility conditions, reaching a maximum airspeed of and Mach 2.3. The rocket performed a soft landing with two parachutes and can be reused. Flight data and engine performance data are published and analyzed. The flight data show excellent stability of the rocket. Engine performance data prove very high efficiency and stable combustion. The subsystem design and verification before the launch is reported. Engine and flight trajectory simulations show very good agreement with the flight data. Furthermore, the overall project, rocket design, and subsystems, as well as the launch campaign, are presented here in detail.

Experimental study of passive air condition system integrated into a single room in Assiut, Egypt

Cooling of buildings is an essential target for engineers and builders in the hot arid climate of Egypt. Performance of inclined solar chimney with passive cooling tower (SCPC) was studied. The system was integrated into a single room built in Assiut University (El-Gorib site) in Assiut, Egypt. Testing of indoor environment for the room with passive cooling was done during August and September 2015. A passive cooling technique was integrated inside a short wind tower made from expanded paper (wet pad) 0.1m thick. A water tube was installed on the top of the expanded paper with small nozzles. Water is recirculated through the system using water pump. A reduction of room indoor temperature was observed with the integrated system (SCPC). There is a significant reduction of indoor temperature between 6 and 7K due to passive cooling with surface temperature 19.4°C for the cooling pad. The relative humidity did not exceed 57% most of the time. The maximum air speed inside the solar chimney was 3.5m/s under the effect of a high solar radiation of 890W/m2. The findings show that SCPC system achieves comfortable thermal conditions with a significant improvement in building energy conservation. The result of development this new cooling system helps to develop building code for low energy houses in Egypt and propose a new system to be integrated in the housing project of people with low income.

Three-dimensional model of air speed in the secondary zone of displacement ventilation jet

This paper presents a new three-dimensional model for the distribution of air speed in the secondary zone of a displacement ventilation jet, combining both physical analysis and correlations-based models. For this purpose the measurements on two wall-mounted DV diffusers are used along with other published data. The maximum air speed at the end of primary zone is predicted by using the supplying conditions at the outlet, the thickness of air jet at the end of the primary zone, and the air entrainment in the jet. The longitudinal profile of maximum air speed in secondary zone is modeled using a new normalization and a generalized profile developed using correlation-based models obtained from experimental data. The vertical and transversal air speed profiles are also presented and analyzed. Finally all air speed profiles in the secondary zone are combined into a three-dimensional air speed model in the DV jet.

DESIGNING ZONING OF REMOTE SENSING DRONES FOR URBAN APPLICATIONS: A REVIEW

Abstract. This paper discusses on-going research related to zoning regulation for the remote sensing drone in the urban applications. Timestamped maps are presented here follow a citation-based approach, where significant information is retrieved from the scientific literature. The emergence of drones in domestic air raises lots understandable issues on privacy, security and uncontrolled pervasive surveillance that require a careful and alternative solution. The effective solution is to adopt a privacy and property rights approach that create a drone zoning and clear drone legislatures. In providing a differential trend to other reviews, this paper is not limited to drones zoning and regulations, but also, discuss on trend remote sensing drones specification in designing a drone zones. Remote sensing drone will specific according to their features and performances; size and endurance, maximum airspeed and altitude level and particular references are made to the drones range. The implementation of laws zoning could lie with the urban planners whereby, a zoning for drone could become a new tactic used to specify areas, where drones could be used, will provide remedies for the harm that arise from drones, and act as a different against irresponsible behaviour. Finally, underlines the need for next regulations on guidelines and standards which can be used as a guidance for urban decision makers to control the drones' operating, thus ensuring a quality and sustainability of resilience cities simultaneously encouraging the revolution of technology.

DESIGNING ZONING OF REMOTE SENSING DRONES FOR URBAN APPLICATIONS: A REVIEW

This paper discusses on-going research related to zoning regulation for the remote sensing drone in the urban applications. Timestamped maps are presented here follow a citation-based approach, where significant information is retrieved from the scientific literature. The emergence of drones in domestic air raises lots understandable issues on privacy, security and uncontrolled pervasive surveillance that require a careful and alternative solution. The effective solution is to adopt a privacy and property rights approach that create a drone zoning and clear drone legislatures. In providing a differential trend to other reviews, this paper is not limited to drones zoning and regulations, but also, discuss on trend remote sensing drones specification in designing a drone zones. Remote sensing drone will specific according to their features and performances; size and endurance, maximum airspeed and altitude level and particular references are made to the drones range. The implementation of laws zoning could lie with the urban planners whereby, a zoning for drone could become a new tactic used to specify areas, where drones could be used, will provide remedies for the harm that arise from drones, and act as a different against irresponsible behaviour. Finally, underlines the need for next regulations on guidelines and standards which can be used as a guidance for urban decision makers to control the drones' operating, thus ensuring a quality and sustainability of resilience cities simultaneously encouraging the revolution of technology.

Constrained Linear Quadratic Tracker for Optimal Performance Flight

M ODERN autonomous vehicles are able not only to follow certain low-level directives, such as airspeed, altitude, and heading, but also to track computed optimal trajectories in the sense to minimize fuel consumption and time of arrival at a certain waypoint while avoiding collisions with known and unknown obstacles, the terrain and other aerial vehicles. Substantial effort has beenmade recently to develop several techniques to compute optimal constrained trajectories for manned [1] and unmanned aircraft [2,3]. A common characteristic of these methods is their strong dependency on the maneuverability properties of the vehicle under consideration. Variables such as flight-path angle, turning rate, and turning radius are considered as constraints in the related optimization problems. Thus, larger values of flight-path angle and turning rate and a reduced radius of turn are desirable, because these improvements would allow for the operation of the vehicle in a wider set of scenarios. However, the inclusion of performance and maneuverability constraints is often accomplished in terms of maximum and minimum bounds without accounting for the fact that, in an aerial vehicle, optimal performance is always related to airspeed or Mach number [4]. For example, it is unlikely to simultaneously achieve maximum airspeed and maximum turning rate. The aircraft flight envelope, i.e. the combination of all achievable steady-state conditions, is more complex than a simple rectangle formed by minimum and maximum admissible values. Once the flight envelope is properly defined for operational purposes, the next task is the proposal and synthesis of a controller concerned with the defined limitations. This controller function, commonly referred to as an envelope protection system, is now widespread in the aeronautics industry [5] and remains a current topic of research. Unnikrishnan and Prasad [6] presented a protection system inwhich the operational limitations are treated as obstacles to be avoided. Falkena et al. [7] investigated several approaches to the problem of envelope protection, including a nonlinear constrained control law based on model predictive control (MPC). One of the challenges to designing envelope protection systems is the need to predict not only the future steady-state level of the constrained variable but also its transient characteristics, especially the peak value. Thus, a natural approach to this problem takes into consideration constrained control techniques, amethodology that has been validated by numerous studies [8–10]. The key mathematical element of these stable constrained controlmethods is the presence of an invariant set [11]withinwhich the state and input are guaranteed to lie, in accordance with the system constraints, indefinitely. Thus, strategies based on the invariant setmembership of the statevector are adequate to handle the envelope protection problem. Based on the aforementioned problems and current state-of-art solutions, this Note presents a constrained control technique called the constrained linear quadratic tracker (CLQT). The proposed method is a simplified variant of the MPC method known as the feasible target tracking MPC [10]. In addition, a new method to represent theflight envelope is proposed, based on linear inequalities. The denominated polyhedral flight envelope is constructed from the computed solutions of the nonlinear free-body equations with the advantage of providing achievable speed schedules for maximum performance maneuvers, such as maximum climbing flight-path angle, maximum turn rate, or a combination of both. Simulation results of the complete system composed of the polyhedral flight envelope representation and CLQT, using the Acaua test vehicle model (Fig. 1), are obtained in calm and turbulent air. The results demonstrate suitable tracking performance and protection against stall, even in a severely turbulent environment, with a relatively low computational execution time.

Automotive Wind Tunnels

The wind tunnels used for full size cars are explained. The main specifications, maximum air speed, test section dimension, test section types, and wall interference are discussed first. Especially, the effect of adaptive wall test section is introduced. Five-belt moving belt system is shown with some examples next, which is the best ground simulation and most suitable for the cars. Finally, low noise wind tunnels and the improvement of conventional wind tunnels to the low noise type are written. Low noise wind tunnels are very popular today, because they are useful to decrease the wind noise of the cars.

Air distribution in office environment with asymmetric workstation layout using chilled beams

Air flow patterns and mean air speeds were studied under laboratory conditions representing a full scale open-plan office. Three basic conditions were tested: summer, spring/autumn and winter. Chilled beams were used to provide cooling, outdoor air supply and air distribution in the room. The heat sources had a notable influence on the flow pattern in the room causing large scale circulation and affecting the direction of inlet jets. The maximum air speed in the occupied zone was higher than the recommendations. The mean air speed was also high on at the floor level but low on at the head level. The air speed was highest in the summer case under high cooling load. Results indicate that especially with high heat loads, it is difficult to fulfill the targets of the existing standards in practice. Two main sources of draught risk were found: a) downfall of colliding inlet jets causing local maxima of air speed and b) large scale circulation caused by asymmetric layout of chilled beams and heat sources. The first phenomenon can cause local draught risk when the workstation is located in the downfall area. The flow pattern is not stable and the position of draught risk areas can change in time and also due to changes in room heat sources. The second phenomenon can cause more constant high air speeds on at the floor level. CFD-simulation was able to predict the general flow pattern but somewhat overestimated the air speed compared to measurements.