Stay Dry By Driving Faster Top-Down In the Rain

The Physics Behind the Phenomena



Whenever you drive around and that unfortunate spot of rain begins to fall, what do people in convertibles do? Well, any average person would rush to pull over, and make sure that they get the roof up in time. There’s also another method that may interest you in the mission to keep yourself dry…simply drive faster. That can’t possibly work, right? You’d certainly be surprised!

To answer the question in its most basic form; yes you can. If you are able to reach a certain speed (and stay above it), you can get through almost any harsh, downpour in almost any car! It’s all about the aerodynamics of these cars, which allow you to avoid getting all wet and ruining your car’s interior.

 There are a number of different pathways that air takes as it passes over or through your car. These can be referred to as boundary layers and to further figure out how this comes into play, we need to look at said pathways.
 
 The two types of generic airflow prevalent in these conditions are laminar and turbulent, with lamina consisting of high pressure, fast speed, swirling air/wind), and turbulent consisting of the transition from laminar into turbulent. In other words, when laminar airflow begins to thicken at these boundary areas, enlarging the possible area to keep dry.
 

 

 
 
After taking all of this into account, the windscreen is the next piece of this little puzzle. As the windshield has a steep incline over the top of the car, the air has to be forced upwards, moving faster as it does so, and then transforms into turbulent airflow after nearing the windscreen’s end.

As the air reaches this part, it becomes somewhat of a ‘cushion’, allowing the air to travel over our heads and keep the rain off us (and out precious cars). Whenever you slow down however, the ‘cushion’ dissipates due to the deceleration of your car and the turbulent airflow ceases.

To figure out just how fast you have to be going in your car actually depends a lot on what make/model it is and what kind of rake your windscreen possesses. A Miata, for example, has quite a sharp incline in regards to its windscreen, thus allowing you to travel slower and still remain dry, around 50 to 55 mph. If you find yourself on the motorway and it starts to rain, you can easily stay dry and not have to exceed the speed limit!



A Ferrari Daytona, on the other hand, will have a much smaller windscreen, or incline steep, and will be forced to go faster in order to stay dry due to the missing presence of turbulent air and no air boundaries/cushions.

With all of this fantastic, new knowledge, rest assured that if you drive a S2000, MR2, or Miata (among others), all you need to do to stay dry is hit the accelerator!


Article source: https://www.carthrottle.com/post/how-fast-do-you-have-to-drive-a-convertible-with-the-top-down-to-stay-dry/