Aerodynamic and thermal modelling of disc brakes - Challenges and limitations

The brake system is a critical component for any passenger vehicle as its task is to convert the kinetic and potential energy of the vehicle into heat, allowing the vehicle to stop. Heat energy generated must be dissipated into the surroundings in order to prevent brake overheating. Traditionally, a lot of experimental testing is performed to ensure correct brake operation under all possible load scenarios. However, with the development of simulation techniques, many vehicle manufacturers today are looking into partially or completely replacing physical experiments by virtual testing. Such a transition has several substantial benefits, but simultaneously a lot of challenges and limitations need to be addressed and understood for reliable and accurate simulation results. This paper summarizes many of such challenges, discusses the effects that can and cannot be captured, and gives a broader picture of the issues faced when conducting numerical brake cooling simulations

Крестьянские речь и голоса в “Записках охотника” И. С. Тургенева и прозе о крестьянах до отмены крепостного права

The article focuses on the representation of peasant speech in short stories from peasant life published before the abolition of serfdom in 1861. The author shows that throughout the entire period, writers gradually increased the ratio of dialect («regional») words in the speech of peasant characters. The culmination of this trend came in the mid-1850s and correlated, on the one hand, with the rapid development of ethnographic and dialectological knowledge in the Russian Empire, and, on the other hand, with the formation of a trend towards the aesthetic representation of peasants as “others” in juxtaposition to the educated elite. In prose, to make the subjectivity of peasants more embodied, it was necessary to depict their speech as generally understandable to readers, and at the same time — as phonetically and lexically different from it. The degree of such deviation was supposed to be not very significant, and literary critics constantly debated the fine line between ‘typically reliable’ and ‘inadequate’. The article presents various ways of depicting peasant voices and speech in the prose of both canonical (I. S. Turgenev) and peripheral authors (I. I. Zapolsky, A. V. Nikitenko, A. F. Martynov, E. P. Novikov). DOI: 10.31168/2305-6754.2022.11.2.8В статье на обширном материале первой половины XIX в. рассматривается репрезентация крестьянской речи в рассказах из крестьянского быта до отмены крепостного права. Автор показывает, что на протяжении всего указанного периода писатели постепенно увеличивали долю диалектных («областных») слов в речи персонажей из крестьян. Апогей этой тенденции пришелся на середину 1850-х гг. и коррелировал, с одной стороны, с бурным развитием этнографического и диалектологического знания в Российской империи, а с другой — с формированием особого режима эстетической репрезентации крестьян как «других» по отношению к образованной элите. Для наиболее полного раскрытия субъективности и субъектности крестьян в прозе требовалось изображать их речь одновременно и как в целом понятную читателям, и как фонетически и лексически отличную от нее. При этом степень такого отклонения должна была быть не очень существенной, за чем критики следили и постоянно дебатировали тонкую грань между типически достоверным и «неадекватным». Различные варианты репрезентации крестьянских голосов и речи анализируются в статье на материале прозы как канонических (И. С. Тургенева), так и периферийных авторов (И. И. Запольский, А. В. Никитенко, А. Ф. Мартынов, Е. П. Новикова). DOI: 10.31168/2305-6754.2022.11.2.

Replicating Brake Cooling Tests by using Coupled CAE Simulations

The present paper provides an overview of the different steps implemented to develop a simulation procedure which aims at replicating the Alpine descent brake cooling performance test. The Alpine descent brake cooling performance test is a driving scenario where brakes are continuously applied at down-hill driving for a prolong time when going down from a mountain. Results are presented and compared to experimental data obtained from the on-road testing. The comparison shows that the developed method is capable of predicting trends and deltas when doing case studies at concept phase of vehicle development. One of the examples of such studies presented in this paper is the effect of different rim designs on the brake cooling performance

A coupled approach for vehicle brake cooling performance simulations

Advances of CFD methods together with the constant growth of computer capacity enables simulations of complex coupled fluid and thermal problems. One such problem is the evaluation of brake cooling performance. The brake system is a critical component for passenger vehicles and ensuring correct brake operation under all possible load scenarios is a safety issue. An accurate prediction of convection, conduction and radiation heat fluxes for such a complicated system is challenging from modelling as well as numerical efficiency perspectives.This study describes a simulation procedure developed to numerically predict brake system component temperatures during a downhill brake performance test. Such tests have stages of forced and natural convection, and therefore, the airflow is influenced by the temperature changes within the system. For the numerical simulation, a coupled approach is utilized by combining aerodynamic and thermal codes. The aerodynamic code computes the convective heat transfer using a fully-detailed vehicle model in the virtual wind tunnel. The thermal code then uses this data and combines it with conduction and radiation calculations to give an accurate prediction of the component temperatures, which are subsequently used for airflow recalculation. The procedure is described in considerable detail for most parts of the setup.The calculated temperature history results are validated against experimental data and show good agreement. The method allows detailed investigations of distribution and direction of the heat fluxes inside the system, and of how these fluxes are affected by changes in material properties as well as changes in parts within or outside the brake system. For instance, it is shown that convection and especially convection from the inner vanes is the main contributor for the heat dissipation from the brake disc. Finally, some examples of how changing the vehicle design affects the brake cooling performance are also discussed

Analysis of vehicle path tracking ability and lateral stability on a floating bridge under a crosswind

The reconstructed route E39 along the west coast of Norway will provide efficient local and regional transportation for people and goods. Efficient transportation implies safety measures exist, e.g., driving speed limits for adverse weather\ua0condition. This is especially important for structures in open areas, such as long-span bridges. This paper investigates the path tracking ability and lateral stability of two vehicle types – a tractor-semitrailer (TS) and a sport utility vehicle (SUV) – on the Bj\uf8rnafjorden floating bridge considering a 1-year storm\ua0condition. At a speed of 108 km/h, the TS experiences a roll-over risk, and at a speed of 90 km/h, it frequently leaves the traffic lane. At the highest speed, the SUV wheels do not lose contact with the bridge deck, but the vehicle does leave the traffic lane. This implies that a TS driver requires more vehicle handling effort over the floating bridge than an SUV driver. Results suggest that a TS can safely enter the bridge at a low speed (36 km/h) and then accelerate to 72 km/h after travelling 2 km. An SUV entering at a speed of 90 km/h and accelerating to 108 km/h after travelling 0.5 km was found to be safe

Effects of wind loads and floating bridge motion on intercity bus lateral stability

Efficient transportation is an important factor for regional socio-economic growth. Excitations from wind loads and road motions can influence vehicle-driver behaviour in a way that may impair transportation. This is especially true in open areas such as long-span bridges. This paper investigates the influence of wind loads and floating bridge motions on bus lateral stability for the straight concept solution across Bj\uf8rnafjorden in Norway. For thisinvestigation, an 8-degree-of-freedom model of a two-axle coach is used. The defined driver model is based on the pure pursuit path tracking method. The vehicle deviation from the path is found to increase with increasing bus speed. This deviation is significant after the vehicle enters the bridge (e.g., over 0.5 m for a speed of 90 km/h). At 108 km/h, the windward rear wheel loses contact, indicating the potential risk of vehicle roll-over. The mean androot-mean-square values of the handwheel steering angle increase with increasing speed, which might cause difficulty for the driver to control the vehicle. Simulation results suggest that the bus can suitably enter the bridge at a lower speed (e.g., 72 km/h) with the possibility of increasing the speed (up to 90 km/h) after approximately 2 km of travelled distance

Investigation of vehicle ride height and wheel position influence on the aerodynamic forces of ground vehicles

To prevent test vehicles from movement during experiments in modernaerodynamic wind tunnels, fastening struts are typically used for a rigid connection between the model and the force balance underneath the wind tunnel floor. A weakness of this experimental set-up is that such struts limit the vertical movement of the vehicle.By analysing experimental data from the Volvo Cars wind tunnel and corresponding CFD simulations the differences in measurements using struts with and without vertical displacement have been analysed and compared. The model used was a Volvo S60

Investigation of Wheel Ventilation-Drag using a Modular Wheel Design Concept

Passenger car fuel consumption is a constant concern for automotive companies and the contribution to fuel consumption from aerodynamics is well known. Several studies have been published on the aerodynamics of wheels. One area of wheel aerodynamics discussed in some of these earlier works is the so-called ventilation resistance. This study investigates ventilation resistance on a number of 17 inch rims, in the Volvo Cars Aerodynamic Wind Tunnel. The ventilation resistance was measured using a custom–built suspension with a tractive force measurement system installed in the Wheel Drive Units (WDUs). The study aims at identifying wheel design factors that have significant effect on the ventilation resistance for the investigated wheel size. The results show that it was possible to measure similar power requirements to rotate the wheels as was found in previous works. The magnitude of the measured ventilation resistance confirms the conclusion that this effect should be taken into account when designing a wheel. It was found that some of the rim design factors have greater influences on the ventilation resistance than others. It was also shown that one of the investigated rims had lower ventilation resistance than measured for the fully-covered wheel configuration