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Basic Information

drag coefficient, refers to an object (such as aircraft, missiles) and the resistance experienced by the gas pressure and the flow ratio of the reference area, it is a dimensionless quantity.

means a resistance coefficient and frictional resistance generated when the rope through the pulley rope pulley bearing rigidity and resistance, which resistance typically be corrected by a coefficient value, this factor is called drag coefficient, or to use ω f Express.

formula

Cx = X / (qS)

wherein,

Cx: resistance coefficient

X: (same as the resistance to the flow velocity direction, rearward is positive) resistance

q: dynamic pressure, q = ρv * v / 2 (ρ is the air density, v is the flow rate of the gas flow with respect to the object)

S: reference area (area of ​​the wing aircraft generally selected reference area)

oil Glossary

drag coefficient (Fr): refers to the same flow rate, pressure medium flows blocking water flow through the same core with the ratio of the pressure difference of the core. Calculated as:

Fr = △ PG / △ PW

where: △ PG-- blocking a flow rate at flooding process for pressure medium flows.

pressure water flows into the process flow at a flow rate △ Pw--.

rotating body

drag coefficient corresponding to before and after the asymmetry object, there is a front end coefficient, and the rear end of the object motion coefficients in a medium, whereby the overall resistance of the two coefficients determined, particularly resistance to movement resistance detail entries formula, y is the size of the object equation, y 'is the a first derivative, x is the direction of movement. y is a direction perpendicular to the other direction of movement. This factor has been considered positive for the centripetal action of the fluid resistance.

longitudinal side rotating body pressure coefficient

are coefficients relative to the volume, is ring-side pressure x axis 360 degrees, this factor is a scalar value, but if one week ring integral value greater than 0 to lateral pressure, asymmetrically distributed disposition, produce lateral directional flow is zero, the time-integrated non-rotating body.

drag coefficient

in the car is a common measure of automotive design, as it relates to aerodynamics. Drag is the air flow parallel to and with the same force. Automotive vehicle impact resistance coefficient by way of the surrounding air. When designing a new car company car, in addition to considering other performance characteristics, but also consider the car drag coefficient. Aerodynamic drag increases as the square of speed; thus at higher speeds it becomes very important. Reducing vehicle drag coefficient increases the performance of the vehicle, as it relates to the speed and fuel efficiency. There are many different ways to reduce the resistance of the vehicle. Common method of measuring resistance of the vehicle through the resistance region.

Hyundai average drag coefficient is between 0.30 and 0.35. SUV having a generally quadrangular shape, typically up to C _d = 0.35-0.45. Drag coefficient of the vehicle is affected by the shape of the body. Various other characteristics also affects the drag coefficient, and is taken into account in these examples. Some car has a surprisingly high resistance coefficient, but this is to compensate for the amount of lift generated by the vehicle, while others are used to obtain the aerodynamic speed and has a much lower coefficient of drag.

C _d to Some examples are as follows. The figures given are generally the basic model. Some "high performance" model may actually have a higher resistance due to the wider tires, additional spoiler and greater cooling system, as many basic / low power half-size type having a heat sink, the remaining blanking region and cooling the engine compartment to reduce drag.

a given vehicle C _d will vary according to the measured wind tunnel. Has been recorded up to 5% change in technology and changes in the test and analysis can also be changed. Thus, if measured at a different tunnel resistance coefficient C _d = 0.30 in the same car, it may be from C < / i> _d = 0.285 to C _d = anywhere 0.315 in.

Gobi surface

Gobi is one of aeolian erosion landforms widely distributed in arid zones, in geological time was one of the activities of sand and dust storms are the main source. During the development of wind erosion desert surfaces, the erodable material (sand) Erosion decreased by long-term, and not corrosion substance (mainly gravel) relative enrichment, not forming a protective layer of gravel etching effect on the underlying material eleven Gobi Deflation plane L? I. Although inhibition of desert sand erosion face activities are known, but quantitative studies of its aerodynamic behavior of the few. Dimensionless drag coefficient reflects the retarding effect of the airflow obstruction of airflow resistance coefficient desert sand surface activity may reflect underlying sand and dust Gobi release active interface strength, and thus can be used to evaluate the aerodynamic surface of the wind erosion desert chemical stability. surface resistance coefficient specific conditions to be observed by a simulation or field determined. However, more complex field conditions, the drag coefficient is only related to the desert surface geometric characteristics of the outer surface of the gravel bed, it is still affected by the topography, It is not difficult to find the ideal topography observation affected place, it is difficult to precisely distinguish the influence from the observation results and gravel covered undulating terrain. Furthermore, the wild form of gravel complex, difficult to accurately describe geometric features and can not be regulated, it is difficult to determine geometric features of resistance coefficient and gravel quantitative relationship.

gravel cover 1.1-8 times that the drag coefficient increases, increasing the particle size of the factor depends on the coverage of gravel. desert surface drag coefficient gravel with increasing particle size and increased coverage for the gravel of different particle sizes, the drag coefficient with gravel coverage changes obey rules similar, i.e. when the coverage is small, the drag coefficient increases with increasing coverage gravel the process is more obvious, the rate of which increases with increasing the coverage and slowed down when the coverage is greater than 40% gravel 50%}, the drag coefficient increases substantially no gravel coverage increases, the bed described desert face i.e. blockade feedback airflow to stabilize, the interface until balance air bed.

when the air flow through the desert surface, the total resistance to gas flow may be decomposed into inter resistance and gravel gravel produced bare surface resistance generated, the resistance coefficient can be expressed as

< section>wherein C _dt is the total drag coefficient, C _dg drag coefficient gravel produced, C _db gravel drag coefficient between the exposed surface produced.

on formula may be over interpreted as: drag coefficient when the desert surface to a constant wind erosion constant established. It is believed that among the already stabilized gravel desert wind erosion add gravel surface is in all of the gravel has been protected, the new drag coefficient increases gravel produced tends to zero. Therefore, the drag coefficient to a constant (equivalent to maximum drag coefficient) criteria may be kinetically stable air tends to wind erosion as desert surface. for the various experiments the gravel, 40% -50% of the surface of the desert wind erosion mature, stable critical coverage.