| 1. |
- Berg, Jan, et al.
(författare)
-
Adapting audio quality assessment procedures for engineering practice
- 2016
-
Ingår i: 139th Audio Engineering Society International Convention. - New York : Audio Engineering Society, Inc.. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- Audio quality is of concern up and down the production chain from content creation to distribution. The technologies employed at each step - equipment, processors like codecs, downmix algorithms and loudspeakers - all are scrutinized for their impact. The now well-established field of audio quality research has developed robust methods for assessments. To form a basis for this work, research has investigated how perceptual dimensions are formed and expressed. The literature includes numerous sonic attributes that may be used to evaluate audio quality. All together, these findings have provided benchmarks and guidelines for improving audio technology, setting standards in the manufacture of sound and recording equipment, and furthering the design of reproduction systems and spaces. They are, however, by comparison rarely used to inform recording and mixing practice. In this paper quality evaluation and mixing practice are compared on selected counts and observations are made on what points these fields may mutually inform one another.
|
|
| 2. |
- Brandt, L.uca, et al.
(författare)
-
Numerical study of turbulent channel flow laden with finite-size non-spherical particles
- 2017
-
Ingår i: 10th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2017. - : International Symposium on Turbulence and Shear Flow Phenomena, TSFP10. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- We present interface-resolved numerical simulations of turbulent channel flow laden with non-spherical rigid and neutrally-buoyant particles. We first focus on the case of oblate particles of aspect ratio 1/3 at volume fractions up to 15% and show that the turbulent drag is decreasing when increasing the particle volume fraction although the effective viscosity of the suspension actually increases. We relate the observed drag reduction to turbulence attenuation and to particle migration away from the near-wall region. Particles tend to align parallel to the wall with rotation rates significantly lower than those reported for spheres. In the second part of the study, we examine the effect of the particle slenderness on the observed drag reduction and show that the drag increases for flatter particles.
|
|
| 3. |
- Canton, Jacopo, et al.
(författare)
-
Linear stability of the flow in a toroidal pipe
- 2015
-
Ingår i: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015. - : TSFP-9. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- While hydrodynamic stability and transition to turbulence in straight pipes - being one of the most fundamental problems in fluid mechanics - has been studied extensively, the stability of curved pipes has received less attention. In the present work, the first (linear) instability of the canonical flow inside a toroidal pipe is investigated as a first step in the study of the related laminar-turbulent transition process. The impact of the curvature of the pipe, in the range 8 e [0.002,1], on the stability properties of the flow is studied in the framework of linear stability analysis. Results show that the flow is indeed modally unstable for all curvatures investigated and that the wave number corresponding to the critical mode depends on the curvature, as do several other features of this problem. The critical modes are mainly located in the region of the Dean vortices, and are characterised by oscillations which are symmetric or antisymmetric as a function of the curvature. The neutral curve associated with the first bifurcation is the result of a complex interaction between isolated modes and branches composed by several modes characterised by a common structure. This behaviour is in obvious contrast to that of straight pipes, which are linearly stable for all Reynolds numbers.
|
|
| 4. |
- Fjällman, Johan, et al.
(författare)
-
Exhaust flow pulsation effect on radial turbine performance
- 2015
-
Ingår i: 11th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2015. - : European Conference on Turbomachinery (ETC). - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- In the current vehicle manufacturing world the chase for a better fuel economy and better driveability is in high gear. One way of doing so is to investigate and optimize the turbocharger. In this paper the flow in a radial turbine of a passenger car turbocharger has been analysed by Large Eddy Simulations. The current simulations have investigated the effects of changing the inlet pulse frequency and inlet pulse shape on turbine's performance parameters (e.g. efficiency, shaft power, pressure distributions). Three different engine speeds and two different pulse shapes were chosen to be compared and analysed. With the total mass flow per pulse being constant for all cases there is a clear dependence of both pulse shape and frequency when it comes to e.g. wheel momentum. Higher frequency increases the peak momentum more than the minimum level. A reduction in pulse duration also increases peak momentum more than the minimum.
|
|
| 5. |
- Fransson, Jens H. M., 1973-, et al.
(författare)
-
Skin-friction drag reduction using the method of spanwise mean velocity gradient
- 2015
-
Ingår i: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015. - : TSFP-9. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- Over the last decade wind tunnel experiments and numerical simulations have shown that steady spanwise mean velocity gradients are able to attenuate the growth of different types of boundary layer disturbances if introduced in a controlled way. In this paper some different techniques to setup the spanwise mean velocity variations are discussed and their stabilizing effect leading to transition delay are quantified. This control strategy has potential to lead to an unforeseen positive impact on the broad spectrum of industrial applications where reducing drag is a daily challenge.
|
|
| 6. |
- Försth, Michael, et al.
(författare)
-
Characterization of the thermal exposure in the en 50399 cable test apparatus
- 2015
-
Ingår i: Fire and Materials 2015, 2-4 Feb 2015, San Francisco, USA. - : Interscience Communications. - 9780000000002 ; , s. 23-37
-
Konferensbidrag (refereegranskat)abstract
- The EN 50399 cable test is used for classification of cables within the European construction products regulation. Means to predict a cables performance in this test, based on material data and small scale test results is of great value for the development of new cable materials. A first step in developing a prediction tool should be to understand the heat exposure on the cables in the EN 50399 test apparatus. The heat load in e.g. the cone calorimeter is very well characterized whereas for EN 50399 only the burner power (20.5 kW) is known. In the cone calorimeter the heating is solely by radiation, whereas for the EN 50399 test a large fraction of the heat exposure depends on feed-back from the cable fire. This paper presents a measuring method for characterizing the thermal exposure inside the EN 50399 cable test apparatus without cables and with a cable rated Euroclass Dca. A new instrument for measuring thermal exposure simultaneously in several directions was developed for the purpose, and thereby the non-isotropic exposure on the cables at different position on the ladder could be investigated
|
|
| 7. |
- Kametani, Yukinori, et al.
(författare)
-
Drag reduction in spatially developing turbulent boundary layers by blowing at constant mass-flux
- 2015
-
Ingår i: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015. - : TSFP-9. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- A series of large-eddy simulations of spatially developing turbulent boundary layers with uniform blowing at moderate Reynolds numbers (based on free-stream velocity, U∞ and momentum thickness, θ) up to Reθ ∼ 2500 were performed with the special focus on the effect of intermittent (separated in streamwise direction) blowing sections. The number of blowing sections, N, investigated is set to be 3, 6, 20, 30 and compared to N = 1, which constitutes the reference case, while the total wall-mass flux is constrained to be the same for all considered cases, corresponding to a blowing amplitude of 0.1% of U∞ for the reference case. Results indicate that the reference case provides a net-energy saving rate of around 18%, which initially decreases at most 2 percentage points for N = 3 but recovers with increasing N. The initial reduction of the drag reduction is due to the shorter streamwise length of intermittent blowing sections. The physical decomposition of the skin friction drag through the FIK identity (Fukagata et at, 2002), shows that the distribution of all components over each blowing section has similar trends, resulting in similar averaged values over the whole control region.
|
|
| 8. |
- Larsson, Ulf, et al.
(författare)
-
Comparison of ventilation performance of three different air supply devices - A measurement study
- 2015
-
Ingår i: Ventilation 2015. - : International Conference on Industrial Ventilation. - 9780000000002 ; , s. 359-366
-
Konferensbidrag (refereegranskat)abstract
- People today spend a significant part of their time in an indoor environment, whether it be home, school, vehicle or workplace. This has put greater demands on indoor air, in terms of both air quality and thermal comfort. The main objective of building ventilation is to take care of pollutants and lower their concentration, but it is also used to cool or heat indoor air. However, exchanging air in a room creates indoor air movements, which can have a major influence on the perception of thermal comfort inside the building. The use of ventilation systems also affects energy use and CO2 discharge to the environment. Therefore it is important to optimize the ventilation system with respect to both indoor climate and energy demand. The aim of this paper was to study the behavior of three different ventilation supply systems, i.e., mixing supply device, displacement supply device and confluent jet supply device, in an office room. The measurements for the present paper were carried out in a special test room at the University of Gￜￜvle, Sweden. The room is well insulated and specially designed for full-scale experiments. The size of the room corresponds to a normal office, to produce a heat-load corresponding to an occupied office room with a computer and a person-simulator placed in the middle of the room. The lighting system was working inside the office room during all the experiments. Twelve different cases have been studied experimentally with different airflow rates, supply air temperature and supply devices. The results show that the confluent jets ventilation with the device placed at 2.2 m provides the highest value of ventilation efficiency, followed by displacement ventilation, while the lowest ventilation efficiency is found in the mixing ventilation system. The temperature gradient looks like what one can expect for both mixing and displacement, and confluent jet is a combination of these two. The results also show that the confluent jets ventilation system provides lower air temperature in the occupied zone compared to both displacement and mixing ventilation.
|
|
| 9. |
- Lazeroms, Werner, et al.
(författare)
-
Nonlinear features in explicit algebraic models for turbulent flows with active scalars
- 2015
-
Ingår i: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015. - : TSFP-9. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- A detailed discussion of explicit algebraic turbulence models in the case of active scalars is given. In particular, we discuss the appearance of nonlinearities in the models and the need for explicit solutions of the resulting nonlinear equations. Focussing on a recently published model for two-dimensional stratified flows, we present an intuitive way of approximating the solution of a sixth-order polynomial equation for the production-to-dissipation ratio (p + g)/e of turbulent kinetic energy K. This formulation is shown to be consistent for turbulent channel flow with stable and unstable stratification. The result is important for obtaining a robust model with a correct behaviour of the turbulence production in different limits of shear and buoyancy. The results have recently been published in Lazeroms et al. (2015).
|
|
| 10. |
- Noorani, Azad, et al.
(författare)
-
Swirl-switching phenomenon in turbulent flow through toroidal pipes
- 2015
-
Ingår i: 9th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2015. - : TSFP-9. - 9780000000002
-
Konferensbidrag (refereegranskat)abstract
- Direct numerical simulations (DNS) are performed to investigate turbulent flows in toroidal pipes with mild and strong curvature. By means of proper orthogonal decomposition (POD), dominant structures in the flow field are identified. The most energetic structures in the strongly curved pipes (κ = 0.1 and κ = 0.3) are very similar in both configurations studied here. These modes (shape and frequency) also match the coherent structures responsible for swirl switching phenomenon found earlier in experimental and numerical studies of turbulent flow in spatially developing 90° bends with which the current results are compared. The observed swirl switching in toroidal pipes, which is isolated from any upstream and separation conditions, may challenge the current hyphothesis regarding the origin of swirl switching mechanism.
|
|
