わ〜わ

わ is an adverbial particle that is commonly used in cases of stress of emphasis in Japanese. When appearing after the dictionary form of a verb that is being repeated, it highlights a large amount, something happening successively, or more and more. It will often be translated as 'more and more (A)', '(A) keeps on happening', or 'so much (A)'. わ～わ may be used either positively or negatively.
To use this structure, simply place わ after the verb, and then repeat the same verb with a second わ.

• もう、昨日(きのう)子供達(こどもたち)が喧嘩(けんか)して泣(な)くわ泣(な)くわで大変(たいへん)だったんだから。
  Oh my god, it was so hectic yesterday because the kids got into a fight and cried so much.
• 空(あ)き家(や)を買(か)ったのはいいけど、家中(いえじゅう)にはゴキブリがいるわいるわ。多分(たぶん)自分(じぶん)じゃ何(なん)もできないから業者(ぎょうしゃ)に頼(たの)むしかなさそう。
  I bought a vacant house, and that's exciting, but there are so many cockroaches all over the house. I probably won't be able to do anything myself, so I will have to call someone.
• 私(わたし)の息子(むすこ)なんて、部活(ぶかつ)を始(はじ)めてからというもの食(た)べるわ食(た)べるわ、食費(しょくし)が心配(しんぱい)だよ。
  Ever since my son has started after school activities, he eats so much that I am worried about the cost of food.

わ～わ primarily emphasizes the speaker's surprise in regard to the amount or extent of (A). This structure is predominantly used by men, but it may also sometimes be used by women. However, there are several different variations of わ depending on where they appear in sentences, each of which have gender usage tendencies that will need to be learned.
In many cases where a する verb is being used with わ～わ, the second instance of the action will be omitted, with する appearing by itself. For example, instead of 勉強(べんきょう)するわ勉強(べんきょう)するわ, 勉強(べんきょう)するわするわ would be used.

• あの子(こ)は医者(いしゃ)になりたいって決(き)めてから、毎日(まいにち)勉強(べんきょう)するわするわ。
  Ever since he has decided that he wants to be a doctor, he studies a lot.